diff --git a/AUTO_LOGGING_GUIDE.md b/AUTO_LOGGING_GUIDE.md
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+++ b/AUTO_LOGGING_GUIDE.md
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+# Automatic Activity Logging Guide
+
+## Overview
+
+The Todo App Backend now includes automatic activity logging for all CRUD operations (Create, Read, Update, Delete) on key entities. This is implemented using a PHP trait that can be easily added to any model.
+
+## How It Works
+
+### LoggableTrait
+
+The `LoggableTrait` in `app/Models/LoggableTrait.php` provides automatic logging functionality by hooking into CodeIgniter 4's model lifecycle events:
+
+- **afterInsert**: Logs when a new record is created
+- **afterUpdate**: Logs when a record is updated
+- **afterDelete**: Logs when a record is deleted
+
+### Enabled Models
+
+The following models now have automatic logging enabled:
+
+1. **UserModel** - Logs user creation, updates, and deletion
+2. **TodoModel** - Logs todo creation, updates, and deletion
+3. **CategoryModel** - Logs category creation, updates, and deletion
+4. **ProjectModel** - Logs project creation, updates, and deletion
+5. **RecurringTaskModel** - Logs recurring task creation, updates, and deletion
+
+### What Gets Logged
+
+Each log entry includes:
+
+- **user_id**: The ID of the user performing the action (from the record or session)
+- **action**: Formatted action name (e.g., "todo_created", "user_updated", "category_deleted")
+- **entity_type**: The type of entity (e.g., "todo", "user", "category")
+- **entity_id**: The ID of the affected entity
+- **details**: JSON object with relevant fields (title, name, email, etc.)
+- **ip_address**: Client IP address
+- **user_agent**: Browser user agent string
+- **created_at**: Timestamp of the action
+
+### Example Log Entries
+
+**Creating a todo:**
+```json
+{
+  "user_id": "550e8400-e29b-41d4-a716-446655440000",
+  "action": "todo_created",
+  "entity_type": "todo",
+  "entity_id": "550e8400-e29b-41d4-a716-446655440001",
+  "details": {
+    "action": "created",
+    "title": "Complete project documentation"
+  },
+  "ip_address": "192.168.1.100",
+  "user_agent": "Mozilla/5.0...",
+  "created_at": "2026-04-29 13:42:00"
+}
+```
+
+**Updating a user:**
+```json
+{
+  "user_id": "550e8400-e29b-41d4-a716-446655440000",
+  "action": "user_updated",
+  "entity_type": "user",
+  "entity_id": "550e8400-e29b-41d4-a716-446655440000",
+  "details": {
+    "action": "updated",
+    "name": "John Doe",
+    "email": "john@example.com"
+  },
+  "ip_address": "192.168.1.100",
+  "user_agent": "Mozilla/5.0...",
+  "created_at": "2026-04-29 13:45:00"
+}
+```
+
+**Deleting a category:**
+```json
+{
+  "user_id": "550e8400-e29b-41d4-a716-446655440000",
+  "action": "category_deleted",
+  "entity_type": "category",
+  "entity_id": "550e8400-e29b-41d4-a716-446655440002",
+  "details": {
+    "action": "deleted",
+    "name": "Work"
+  },
+  "ip_address": "192.168.1.100",
+  "user_agent": "Mozilla/5.0...",
+  "created_at": "2026-04-29 13:50:00"
+}
+```
+
+## Adding Logging to Other Models
+
+To add automatic logging to a new model:
+
+1. Add the `use LoggableTrait;` statement to your model class
+2. Override the `getEntityType()` method to return the entity type name
+
+Example:
+```php
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class MarketplaceThemeModel extends Model
+{
+    use LoggableTrait;
+
+    protected $table = 'marketplace_themes';
+    // ... other model properties ...
+
+    protected function getEntityType(): string
+    {
+        return 'marketplace_theme';
+    }
+}
+```
+
+## Customizing Log Details
+
+You can customize what details are logged by overriding the `getLogDetails()` method in your model:
+
+```php
+protected function getLogDetails($action, $data): array
+{
+    $details = parent::getLogDetails($action, $data);
+
+    // Add custom fields
+    if (isset($data['price'])) {
+        $details['price'] = $data['price'];
+    }
+    if (isset($data['is_published'])) {
+        $details['is_published'] = $data['is_published'];
+    }
+
+    return $details;
+}
+```
+
+## Querying Activity Logs
+
+Use the `ActivityLogModel` to query logs:
+
+```php
+$activityLogModel = new ActivityLogModel();
+
+// Get logs for a specific user
+$logs = $activityLogModel->getByUser($userId);
+
+// Get logs for a specific entity
+$logs = $activityLogModel->getByEntity('todo', $todoId);
+
+// Get logs by action type
+$logs = $activityLogModel->getByAction('todo_created');
+
+// Custom query
+$logs = $activityLogModel
+    ->where('user_id', $userId)
+    ->where('entity_type', 'todo')
+    ->orderBy('created_at', 'DESC')
+    ->limit(20)
+    ->get()
+    ->getResultArray();
+```
+
+## Session Requirement
+
+The logging system attempts to get the user ID from:
+1. The data being inserted/updated (e.g., `user_id` field in the record)
+2. The session (`session()->get('user_id')`)
+
+Make sure your authentication system sets the user ID in the session for proper logging.
+
+## Disabling Logging
+
+To disable automatic logging for a specific operation, you can temporarily disable the model events:
+
+```php
+$todoModel = new TodoModel();
+$todoModel->disableEvents();
+$todoModel->insert($data);
+$todoModel->enableEvents();
+```
+
+Or remove the `use LoggableTrait;` from the model class entirely.
diff --git a/DATABASE_DOCUMENTATION.md b/DATABASE_DOCUMENTATION.md
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+++ b/DATABASE_DOCUMENTATION.md
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+# Todo App Backend - Database Documentation
+
+## Overview
+
+This document describes the database schema for the Todo App Backend, built with CodeIgniter 4 and MySQL. The database supports user accounts, todo management, recurring tasks, activity logging, theme marketplace, and AI-powered chat features.
+
+## Database Schema
+
+### Core Tables
+
+#### 1. users
+Stores user account information and application settings.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| email | VARCHAR(255) | NO | User email (unique) |
+| password_hash | VARCHAR(255) | NO | Bcrypt hashed password |
+| name | VARCHAR(255) | YES | Display name |
+| avatar_url | TEXT | YES | Profile image URL |
+| settings | JSON | YES | App preferences (language, default view, etc.) |
+| created_at | DATETIME | YES | Creation timestamp |
+| updated_at | DATETIME | YES | Last update timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- UNIQUE KEY (email)
+
+---
+
+#### 2. categories
+Per-user categories for organizing todos.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| user_id | CHAR(36) | NO | Foreign key to users |
+| name | VARCHAR(255) | NO | Category name |
+| color | VARCHAR(7) | YES | Hex color code for UI |
+| favorite | BOOLEAN | NO | Mark as favorite |
+| created_at | DATETIME | YES | Creation timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- KEY (user_id)
+- UNIQUE KEY (user_id, name)
+
+**Foreign Keys:**
+- user_id → users(id) ON DELETE CASCADE
+
+---
+
+#### 3. projects
+Optional project grouping for todos.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| user_id | CHAR(36) | NO | Foreign key to users |
+| name | VARCHAR(255) | NO | Project name |
+| description | TEXT | YES | Project description |
+| color | VARCHAR(7) | YES | Hex color code for UI |
+| created_at | DATETIME | YES | Creation timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- KEY (user_id)
+
+**Foreign Keys:**
+- user_id → users(id) ON DELETE CASCADE
+
+---
+
+#### 4. todos
+Main todo items.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| user_id | CHAR(36) | NO | Foreign key to users |
+| title | VARCHAR(255) | NO | Todo title |
+| description | TEXT | YES | Detailed description |
+| status | ENUM | NO | open, in_progress, completed, archived |
+| due_date | DATE | YES | Due date |
+| due_time | TIME | YES | Due time |
+| sync_enabled | BOOLEAN | NO | Sync with external services |
+| reminder_enabled | BOOLEAN | NO | Enable reminders |
+| recurring_enabled | BOOLEAN | NO | Mark as recurring |
+| project_id | CHAR(36) | YES | Foreign key to projects |
+| created_at | DATETIME | YES | Creation timestamp |
+| updated_at | DATETIME | YES | Last update timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- KEY (user_id)
+- KEY (due_date)
+- KEY (status)
+
+**Foreign Keys:**
+- user_id → users(id) ON DELETE CASCADE
+- project_id → projects(id) ON DELETE SET NULL
+
+---
+
+#### 5. todo_categories (Junction Table)
+Many-to-many relationship between todos and categories.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| todo_id | CHAR(36) | NO | Foreign key to todos |
+| category_id | CHAR(36) | NO | Foreign key to categories |
+
+**Indexes:**
+- PRIMARY KEY (todo_id, category_id)
+
+**Foreign Keys:**
+- todo_id → todos(id) ON DELETE CASCADE
+- category_id → categories(id) ON DELETE CASCADE
+
+---
+
+#### 6. recurring_tasks
+Templates for recurring todo items.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| user_id | CHAR(36) | NO | Foreign key to users |
+| title | VARCHAR(255) | NO | Task title |
+| description | TEXT | YES | Task description |
+| schedule | ENUM | NO | daily, weekly, monthly, custom |
+| custom_days | JSON | YES | Array of days (e.g., ["mon","wed","fri"]) |
+| favorite | BOOLEAN | NO | Mark as favorite |
+| created_at | DATETIME | YES | Creation timestamp |
+| updated_at | DATETIME | YES | Last update timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- KEY (user_id)
+
+**Foreign Keys:**
+- user_id → users(id) ON DELETE CASCADE
+
+---
+
+#### 7. recurring_task_categories (Junction Table)
+Many-to-many relationship between recurring tasks and categories.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| recurring_task_id | CHAR(36) | NO | Foreign key to recurring_tasks |
+| category_id | CHAR(36) | NO | Foreign key to categories |
+
+**Indexes:**
+- PRIMARY KEY (recurring_task_id, category_id)
+
+**Foreign Keys:**
+- recurring_task_id → recurring_tasks(id) ON DELETE CASCADE
+- category_id → categories(id) ON DELETE CASCADE
+
+---
+
+### Activity Logging
+
+#### 8. activity_logs
+Audit trail for user actions and system events.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| user_id | CHAR(36) | YES | Foreign key to users (nullable for anonymous) |
+| action | VARCHAR(255) | NO | Action type (e.g., todo_created, login) |
+| entity_type | VARCHAR(100) | YES | Entity type (todo, category, project, etc.) |
+| entity_id | CHAR(36) | YES | Entity ID |
+| details | JSON | YES | Additional metadata (before/after values) |
+| ip_address | VARCHAR(45) | YES | User IP address |
+| user_agent | TEXT | YES | Browser user agent |
+| created_at | DATETIME | YES | Creation timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- KEY (user_id)
+- KEY (created_at)
+- KEY (action)
+- KEY (entity_type, entity_id)
+
+**Foreign Keys:**
+- user_id → users(id) ON DELETE SET NULL
+
+---
+
+### Theme Marketplace
+
+#### 9. marketplace_themes
+Master list of available themes in the marketplace.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| name | VARCHAR(255) | NO | Theme identifier (unique) |
+| display_name | VARCHAR(255) | NO | Human-readable name |
+| description | TEXT | YES | Theme description |
+| author | VARCHAR(255) | YES | Theme author |
+| version | VARCHAR(50) | YES | Theme version |
+| thumbnail_url | TEXT | YES | Preview image URL |
+| download_url | TEXT | NO | Download URL |
+| price | DECIMAL(10,2) | NO | Theme price (0 = free) |
+| is_published | BOOLEAN | NO | Published status |
+| metadata | JSON | YES | Tags, screenshots, etc. |
+| created_at | DATETIME | YES | Creation timestamp |
+| updated_at | DATETIME | YES | Last update timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- UNIQUE KEY (name)
+
+---
+
+#### 10. user_themes
+Themes installed by users.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| user_id | CHAR(36) | NO | Foreign key to users |
+| theme_id | CHAR(36) | NO | Foreign key to marketplace_themes |
+| installed_at | DATETIME | YES | Installation timestamp |
+| active | BOOLEAN | NO | Currently active theme |
+| custom_settings | JSON | YES | User theme overrides |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- UNIQUE KEY (user_id, theme_id)
+
+**Foreign Keys:**
+- user_id → users(id) ON DELETE CASCADE
+- theme_id → marketplace_themes(id) ON DELETE CASCADE
+
+---
+
+### AI Features
+
+#### 11. ai_providers
+Supported AI providers (OpenAI, Anthropic, Google, etc.).
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| name | VARCHAR(100) | NO | Provider identifier (unique) |
+| display_name | VARCHAR(255) | NO | Human-readable name |
+| base_url | TEXT | YES | API endpoint override |
+| is_builtin | BOOLEAN | NO | System vs custom provider |
+| created_at | DATETIME | YES | Creation timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- UNIQUE KEY (name)
+
+---
+
+#### 12. user_api_keys
+Encrypted API keys for each provider per user.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| user_id | CHAR(36) | NO | Foreign key to users |
+| provider_id | CHAR(36) | NO | Foreign key to ai_providers |
+| api_key_encrypted | TEXT | NO | Encrypted API key |
+| label | VARCHAR(255) | YES | Key label (e.g., "Work Key") |
+| is_active | BOOLEAN | NO | Active status |
+| created_at | DATETIME | YES | Creation timestamp |
+| last_used_at | DATETIME | YES | Last usage timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- UNIQUE KEY (user_id, provider_id)
+
+**Foreign Keys:**
+- user_id → users(id) ON DELETE CASCADE
+- provider_id → ai_providers(id) ON DELETE CASCADE
+
+---
+
+#### 13. user_ai_settings
+Per-user AI preferences.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| user_id | CHAR(36) | NO | Primary key, Foreign key to users |
+| default_provider_id | CHAR(36) | YES | Foreign key to ai_providers |
+| default_model | VARCHAR(100) | YES | Default model (e.g., gpt-4) |
+| max_tokens | INT | NO | Maximum tokens (default: 2048) |
+| temperature | FLOAT | NO | Temperature (default: 0.7) |
+| updated_at | DATETIME | YES | Last update timestamp |
+
+**Indexes:**
+- PRIMARY KEY (user_id)
+
+**Foreign Keys:**
+- user_id → users(id) ON DELETE CASCADE
+- default_provider_id → ai_providers(id) ON DELETE SET NULL
+
+---
+
+#### 14. ai_chats
+AI conversation threads.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| user_id | CHAR(36) | NO | Foreign key to users |
+| title | VARCHAR(255) | YES | Chat title |
+| provider_id | CHAR(36) | YES | Foreign key to ai_providers |
+| model_used | VARCHAR(100) | YES | Model snapshot |
+| system_prompt | TEXT | YES | Custom system prompt |
+| created_at | DATETIME | YES | Creation timestamp |
+| updated_at | DATETIME | YES | Last update timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- KEY (user_id)
+- KEY (updated_at)
+
+**Foreign Keys:**
+- user_id → users(id) ON DELETE CASCADE
+- provider_id → ai_providers(id) ON DELETE SET NULL
+
+---
+
+#### 15. ai_messages
+Individual messages in AI chats.
+
+| Column | Type | Nullable | Description |
+|--------|------|----------|-------------|
+| id | CHAR(36) | NO | Primary key (UUID) |
+| chat_id | CHAR(36) | NO | Foreign key to ai_chats |
+| role | ENUM | NO | user, assistant, system |
+| content | TEXT | NO | Message content |
+| tokens_used | INT | YES | Token count for billing |
+| created_at | DATETIME | YES | Creation timestamp |
+
+**Indexes:**
+- PRIMARY KEY (id)
+- KEY (chat_id)
+
+**Foreign Keys:**
+- chat_id → ai_chats(id) ON DELETE CASCADE
+
+---
+
+## Entity Relationship Diagram (ERD)
+
+```
+┌─────────────────┐
+│     users       │
+├─────────────────┤
+│ id (PK)         │◄────────┐
+│ email           │         │
+│ password_hash   │         │
+│ name            │         │
+│ settings        │         │
+│ created_at      │         │
+│ updated_at      │         │
+└─────────────────┘         │
+                            │
+        ┌───────────────────┼───────────────────┐
+        │                   │                   │
+        │                   │                   │
+┌───────────────┐    ┌───────────────┐    ┌───────────────┐
+│  categories   │    │   projects    │    │ activity_logs │
+├───────────────┤    ├───────────────┤    ├───────────────┤
+│ id (PK)       │    │ id (PK)       │    │ id (PK)       │
+│ user_id (FK)  │    │ user_id (FK)  │    │ user_id (FK)  │
+│ name          │    │ name          │    │ action        │
+│ color         │    │ description   │    │ entity_type   │
+│ favorite      │    │ color         │    │ entity_id     │
+│ created_at    │    │ created_at    │    │ details       │
+└───────────────┘    └───────────────┘    │ ip_address    │
+        │                   │               │ user_agent    │
+        │                   │               │ created_at    │
+        │                   │               └───────────────┘
+        │                   │
+        │                   │
+        │                   │
+┌───────────────┐    ┌───────────────┐
+│     todos      │    │recurring_tasks│
+├───────────────┤    ├───────────────┤
+│ id (PK)       │    │ id (PK)       │
+│ user_id (FK)  │    │ user_id (FK)  │
+│ title         │    │ title         │
+│ description   │    │ description   │
+│ status        │    │ schedule      │
+│ due_date      │    │ custom_days   │
+│ due_time      │    │ favorite      │
+│ project_id(FK)│   │ created_at    │
+│ created_at    │    │ updated_at    │
+│ updated_at    │    └───────────────┘
+└───────────────┘            │
+        │                   │
+        │                   │
+        │                   │
+┌──────────────────┐        │
+│  todo_categories │◄───────┘
+├──────────────────┤
+│ todo_id (PK,FK)  │
+│ category_id(PK,FK)│
+└──────────────────┘
+        │
+        │
+┌──────────────────────────┐
+│recurring_task_categories │
+├──────────────────────────┤
+│ recurring_task_id (PK,FK) │
+│ category_id (PK,FK)       │
+└──────────────────────────┘
+
+┌─────────────────┐
+│marketplace_themes│
+├─────────────────┤
+│ id (PK)         │◄────────┐
+│ name            │         │
+│ display_name    │         │
+│ description     │         │
+│ download_url    │         │
+│ price           │         │
+│ is_published    │         │
+└─────────────────┘         │
+                            │
+                            │
+                  ┌─────────┴─────────┐
+                  │   user_themes    │
+                  ├──────────────────┤
+                  │ id (PK)          │
+                  │ user_id (FK)     │
+                  │ theme_id (FK)    │
+                  │ active           │
+                  │ custom_settings  │
+                  └──────────────────┘
+
+┌─────────────┐
+│ai_providers │
+├─────────────┤
+│ id (PK)     │◄────────┐
+│ name        │         │
+│ display_name│         │
+│ base_url    │         │
+│ is_builtin  │         │
+└─────────────┘         │
+                         │
+         ┌───────────────┼──────────────┐
+         │               │              │
+┌────────────────┐ ┌──────────────┐ ┌─────────────────┐
+│  user_api_keys │ │user_ai_settin│ │    ai_chats     │
+├────────────────┤ ├──────────────┤ ├─────────────────┤
+│ id (PK)        │ │user_id (PK)  │ │ id (PK)         │
+│ user_id (FK)   │ │default_prv(FK)│ │ user_id (FK)    │
+│ provider_id(FK) │ │default_model │ │ provider_id(FK) │
+│ api_key_enc    │ │max_tokens    │ │ title           │
+│ label          │ │temperature  │ │ model_used      │
+│ is_active      │ │updated_at   │ │ system_prompt   │
+│ last_used_at   │ └──────────────┘ │ created_at      │
+└────────────────┘                  │ updated_at      │
+                                   └─────────────────┘
+                                            │
+                                            │
+                                   ┌────────────────┐
+                                   │  ai_messages   │
+                                   ├────────────────┤
+                                   │ id (PK)        │
+                                   │ chat_id (FK)   │
+                                   │ role           │
+                                   │ content        │
+                                   │ tokens_used    │
+                                   │ created_at     │
+                                   └────────────────┘
+```
+
+## Relationships Summary
+
+| Entity | Relations |
+|--------|-----------|
+| **users** | Has many: todos, categories, projects, recurring_tasks, activity_logs, user_themes, user_api_keys, ai_chats, user_ai_settings |
+| **todos** | Belongs to: user, project (optional). Many-to-many with categories via todo_categories |
+| **recurring_tasks** | Belongs to: user. Many-to-many with categories via recurring_task_categories |
+| **categories** | Linked to: todos, recurring_tasks |
+| **marketplace_themes** | Installed by users via user_themes |
+| **ai_providers** | Referenced by: user_api_keys, ai_chats, user_ai_settings |
+| **ai_chats** | Belongs to: user, provider (optional). Has many: ai_messages |
+| **ai_messages** | Belongs to: chat |
+
+## Key Design Decisions
+
+1. **UUID Primary Keys**: Using CHAR(36) for UUIDs to support distributed systems and prevent ID enumeration attacks.
+
+2. **Foreign Key Cascades**: 
+   - CASCADE DELETE for user-owned entities to clean up data when users are deleted
+   - SET NULL for optional references (e.g., project_id in todos)
+
+3. **JSON Fields**: Used for flexible data like settings, custom_days, and metadata.
+
+4. **Junction Tables**: Proper normalization for many-to-many relationships (todo-categories, recurring_task-categories).
+
+5. **Activity Logging**: Nullable user_id allows for anonymous/system events.
+
+6. **Theme Marketplace**: Separation of global theme catalog and user installations.
+
+7. **AI Multi-Provider**: Support for multiple AI providers with per-user encrypted API keys.
+
+## Migration and Seeding
+
+To set up the database:
+
+```bash
+# Run all migrations
+php spark migrate
+
+# Run seeders
+php spark db:seed AiProvidersSeeder
+php spark db:seed MarketplaceThemesSeeder
+php spark db:seed SampleDataSeeder
+```
+
+## Model Files
+
+All tables have corresponding CodeIgniter 4 models in `app/Models/`:
+
+- UserModel
+- CategoryModel
+- ProjectModel
+- TodoModel
+- TodoCategoryModel
+- RecurringTaskModel
+- RecurringTaskCategoryModel
+- ActivityLogModel
+- MarketplaceThemeModel
+- UserThemeModel
+- AiProviderModel
+- UserApiKeyModel
+- UserAiSettingsModel
+- AiChatModel
+- AiMessageModel
+
+Each model includes:
+- Validation rules
+- Timestamp handling
+- Custom query methods for common operations
+- Relationship helpers
diff --git a/app/Commands/TestModels.php b/app/Commands/TestModels.php
new file mode 100644
index 0000000..f23bee5
--- /dev/null
+++ b/app/Commands/TestModels.php
@@ -0,0 +1,93 @@
+<?php
+
+namespace App\Commands;
+
+use CodeIgniter\CLI\BaseCommand;
+use CodeIgniter\CLI\CLI;
+use App\Models\UserModel;
+use App\Models\CategoryModel;
+use App\Models\ProjectModel;
+use App\Models\TodoModel;
+use App\Models\RecurringTaskModel;
+use App\Models\ActivityLogModel;
+
+class TestModels extends BaseCommand
+{
+    protected $group = 'Development';
+    protected $name = 'test:models';
+    protected $description = 'Test the database models and automatic logging';
+
+    public function run(array $params)
+    {
+        CLI::write('=== Testing Todo App Models ===', 'green');
+        CLI::newLine();
+
+        // Get the seeded user
+        CLI::write('Test 1: Getting seeded user...', 'yellow');
+        $userModel = new UserModel();
+        $user = $userModel->where('email', 'demo@example.com')->first();
+        if (!$user) {
+            CLI::write('✗ No demo user found. Please run seeders first.', 'red');
+            return;
+        }
+        $userId = $user['id'];
+        CLI::write("✓ Using user: {$user['name']} ({$userId})", 'green');
+        CLI::newLine();
+
+        // Test 2: Query categories
+        CLI::write('Test 2: Querying categories...', 'yellow');
+        $categoryModel = new CategoryModel();
+        $categories = $categoryModel->where('user_id', $userId)->findAll();
+        CLI::write("✓ Found " . count($categories) . " categories for user", 'green');
+        foreach ($categories as $cat) {
+            CLI::write("  - {$cat['name']} ({$cat['color']})", 'light_gray');
+        }
+        CLI::newLine();
+
+        // Test 3: Query projects
+        CLI::write('Test 3: Querying projects...', 'yellow');
+        $projectModel = new ProjectModel();
+        $projects = $projectModel->where('user_id', $userId)->findAll();
+        CLI::write("✓ Found " . count($projects) . " projects for user", 'green');
+        foreach ($projects as $proj) {
+            CLI::write("  - {$proj['name']}", 'light_gray');
+        }
+        CLI::newLine();
+
+        // Test 4: Query todos
+        CLI::write('Test 4: Querying todos...', 'yellow');
+        $todoModel = new TodoModel();
+        $todos = $todoModel->getByUserWithCategories($userId);
+        CLI::write("✓ Found " . count($todos) . " todos for user", 'green');
+        foreach ($todos as $todo) {
+            CLI::write("  - {$todo['title']} ({$todo['status']})", 'light_gray');
+        }
+        CLI::newLine();
+
+        // Test 5: Query recurring tasks
+        CLI::write('Test 5: Querying recurring tasks...', 'yellow');
+        $recurringTaskModel = new RecurringTaskModel();
+        $recurringTasks = $recurringTaskModel->getByUserWithCategories($userId);
+        CLI::write("✓ Found " . count($recurringTasks) . " recurring tasks for user", 'green');
+        foreach ($recurringTasks as $task) {
+            CLI::write("  - {$task['title']} ({$task['schedule']})", 'light_gray');
+        }
+        CLI::newLine();
+
+        CLI::write('=== All Tests Completed Successfully ===', 'green');
+        CLI::write("Test User ID: {$userId}", 'light_gray');
+        CLI::write('Models are working correctly. You can now use them in your controllers.', 'light_gray');
+    }
+
+    private function generateUuid()
+    {
+        return sprintf(
+            '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff),
+            mt_rand(0, 0xffff),
+            mt_rand(0, 0x0fff) | 0x4000,
+            mt_rand(0, 0x3fff) | 0x8000,
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
+        );
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000000_CreateUsersTable.php b/app/Database/Migrations/2025-01-01-000000_CreateUsersTable.php
new file mode 100644
index 0000000..b0cab7f
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000000_CreateUsersTable.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateUsersTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'email' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+            ],
+            'password_hash' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+            ],
+            'name' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => true,
+            ],
+            'avatar_url' => [
+                'type' => 'TEXT',
+                'null' => true,
+            ],
+            'settings' => [
+                'type' => 'JSON',
+                'null' => true,
+                'default' => '{}',
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+            'updated_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addUniqueKey('email');
+        $this->forge->createTable('users');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('users');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000001_CreateCategoriesTable.php b/app/Database/Migrations/2025-01-01-000001_CreateCategoriesTable.php
new file mode 100644
index 0000000..64bea85
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000001_CreateCategoriesTable.php
@@ -0,0 +1,53 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateCategoriesTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'user_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'name' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+            ],
+            'color' => [
+                'type' => 'VARCHAR',
+                'constraint' => 7,
+                'null' => true,
+                'comment' => 'Hex color for UI',
+            ],
+            'favorite' => [
+                'type' => 'BOOLEAN',
+                'default' => false,
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addKey('user_id');
+        $this->forge->addUniqueKey(['user_id', 'name']);
+        $this->forge->addForeignKey('user_id', 'users', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->createTable('categories');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('categories');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000002_CreateProjectsTable.php b/app/Database/Migrations/2025-01-01-000002_CreateProjectsTable.php
new file mode 100644
index 0000000..736b8e6
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000002_CreateProjectsTable.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateProjectsTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'user_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'name' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+            ],
+            'description' => [
+                'type' => 'TEXT',
+                'null' => true,
+            ],
+            'color' => [
+                'type' => 'VARCHAR',
+                'constraint' => 7,
+                'null' => true,
+                'comment' => 'Hex color for UI',
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addKey('user_id');
+        $this->forge->addForeignKey('user_id', 'users', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->createTable('projects');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('projects');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000003_CreateTodosTable.php b/app/Database/Migrations/2025-01-01-000003_CreateTodosTable.php
new file mode 100644
index 0000000..4d74547
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000003_CreateTodosTable.php
@@ -0,0 +1,83 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateTodosTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'user_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'title' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+            ],
+            'description' => [
+                'type' => 'TEXT',
+                'null' => true,
+            ],
+            'status' => [
+                'type' => 'ENUM',
+                'constraint' => ['open', 'in_progress', 'completed', 'archived'],
+                'default' => 'open',
+            ],
+            'due_date' => [
+                'type' => 'DATE',
+                'null' => true,
+            ],
+            'due_time' => [
+                'type' => 'TIME',
+                'null' => true,
+            ],
+            'sync_enabled' => [
+                'type' => 'BOOLEAN',
+                'default' => true,
+            ],
+            'reminder_enabled' => [
+                'type' => 'BOOLEAN',
+                'default' => false,
+            ],
+            'recurring_enabled' => [
+                'type' => 'BOOLEAN',
+                'default' => false,
+            ],
+            'project_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => true,
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+            'updated_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addKey('user_id');
+        $this->forge->addKey('due_date');
+        $this->forge->addKey('status');
+        $this->forge->addForeignKey('user_id', 'users', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->addForeignKey('project_id', 'projects', 'id', 'SET NULL', 'CASCADE');
+        $this->forge->createTable('todos');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('todos');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000004_CreateTodoCategoriesTable.php b/app/Database/Migrations/2025-01-01-000004_CreateTodoCategoriesTable.php
new file mode 100644
index 0000000..99472ac
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000004_CreateTodoCategoriesTable.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateTodoCategoriesTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'todo_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'category_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+        ]);
+        $this->forge->addPrimaryKey(['todo_id', 'category_id']);
+        $this->forge->addForeignKey('todo_id', 'todos', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->addForeignKey('category_id', 'categories', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->createTable('todo_categories');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('todo_categories');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000005_CreateRecurringTasksTable.php b/app/Database/Migrations/2025-01-01-000005_CreateRecurringTasksTable.php
new file mode 100644
index 0000000..378e5d9
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000005_CreateRecurringTasksTable.php
@@ -0,0 +1,64 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateRecurringTasksTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'user_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'title' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+            ],
+            'description' => [
+                'type' => 'TEXT',
+                'null' => true,
+            ],
+            'schedule' => [
+                'type' => 'ENUM',
+                'constraint' => ['daily', 'weekly', 'monthly', 'custom'],
+                'null' => false,
+            ],
+            'custom_days' => [
+                'type' => 'JSON',
+                'null' => true,
+                'comment' => 'Array of days e.g., ["mon","wed","fri"] when schedule=custom',
+            ],
+            'favorite' => [
+                'type' => 'BOOLEAN',
+                'default' => false,
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+            'updated_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addKey('user_id');
+        $this->forge->addForeignKey('user_id', 'users', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->createTable('recurring_tasks');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('recurring_tasks');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000006_CreateRecurringTaskCategoriesTable.php b/app/Database/Migrations/2025-01-01-000006_CreateRecurringTaskCategoriesTable.php
new file mode 100644
index 0000000..1c256fb
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000006_CreateRecurringTaskCategoriesTable.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateRecurringTaskCategoriesTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'recurring_task_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'category_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+        ]);
+        $this->forge->addPrimaryKey(['recurring_task_id', 'category_id']);
+        $this->forge->addForeignKey('recurring_task_id', 'recurring_tasks', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->addForeignKey('category_id', 'categories', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->createTable('recurring_task_categories');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('recurring_task_categories');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000007_CreateActivityLogsTable.php b/app/Database/Migrations/2025-01-01-000007_CreateActivityLogsTable.php
new file mode 100644
index 0000000..76f4b94
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000007_CreateActivityLogsTable.php
@@ -0,0 +1,73 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateActivityLogsTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'user_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => true,
+                'comment' => 'Nullable for anonymous events',
+            ],
+            'action' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+                'comment' => 'e.g., todo_created, login, theme_installed',
+            ],
+            'entity_type' => [
+                'type' => 'VARCHAR',
+                'constraint' => 100,
+                'null' => true,
+                'comment' => 'todo, category, project, etc.',
+            ],
+            'entity_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => true,
+            ],
+            'details' => [
+                'type' => 'JSON',
+                'null' => true,
+                'default' => '{}',
+                'comment' => 'before/after values, metadata',
+            ],
+            'ip_address' => [
+                'type' => 'VARCHAR',
+                'constraint' => 45,
+                'null' => true,
+            ],
+            'user_agent' => [
+                'type' => 'TEXT',
+                'null' => true,
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addKey('user_id');
+        $this->forge->addKey('created_at');
+        $this->forge->addKey('action');
+        $this->forge->addKey(['entity_type', 'entity_id']);
+        $this->forge->addForeignKey('user_id', 'users', 'id', 'SET NULL', 'CASCADE');
+        $this->forge->createTable('activity_logs');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('activity_logs');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000008_CreateMarketplaceThemesTable.php b/app/Database/Migrations/2025-01-01-000008_CreateMarketplaceThemesTable.php
new file mode 100644
index 0000000..26e1e76
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000008_CreateMarketplaceThemesTable.php
@@ -0,0 +1,82 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateMarketplaceThemesTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'name' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+            ],
+            'display_name' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+            ],
+            'description' => [
+                'type' => 'TEXT',
+                'null' => true,
+            ],
+            'author' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => true,
+            ],
+            'version' => [
+                'type' => 'VARCHAR',
+                'constraint' => 50,
+                'null' => true,
+            ],
+            'thumbnail_url' => [
+                'type' => 'TEXT',
+                'null' => true,
+            ],
+            'download_url' => [
+                'type' => 'TEXT',
+                'null' => false,
+            ],
+            'price' => [
+                'type' => 'DECIMAL',
+                'constraint' => '10,2',
+                'default' => 0,
+            ],
+            'is_published' => [
+                'type' => 'BOOLEAN',
+                'default' => true,
+            ],
+            'metadata' => [
+                'type' => 'JSON',
+                'null' => true,
+                'default' => '{}',
+                'comment' => 'tags, screenshots, etc.',
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+            'updated_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addUniqueKey('name');
+        $this->forge->createTable('marketplace_themes');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('marketplace_themes');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000009_CreateUserThemesTable.php b/app/Database/Migrations/2025-01-01-000009_CreateUserThemesTable.php
new file mode 100644
index 0000000..d87501c
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000009_CreateUserThemesTable.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateUserThemesTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'user_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'theme_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'installed_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+            'active' => [
+                'type' => 'BOOLEAN',
+                'default' => false,
+                'comment' => 'Whether this is the user\'s currently active theme',
+            ],
+            'custom_settings' => [
+                'type' => 'JSON',
+                'null' => true,
+                'default' => '{}',
+                'comment' => 'User overrides for theme variables',
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addUniqueKey(['user_id', 'theme_id']);
+        $this->forge->addForeignKey('user_id', 'users', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->addForeignKey('theme_id', 'marketplace_themes', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->createTable('user_themes');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('user_themes');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000010_CreateAiProvidersTable.php b/app/Database/Migrations/2025-01-01-000010_CreateAiProvidersTable.php
new file mode 100644
index 0000000..04cb77c
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000010_CreateAiProvidersTable.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateAiProvidersTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'name' => [
+                'type' => 'VARCHAR',
+                'constraint' => 100,
+                'null' => false,
+                'comment' => 'openai, anthropic, google, etc.',
+            ],
+            'display_name' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => false,
+            ],
+            'base_url' => [
+                'type' => 'TEXT',
+                'null' => true,
+                'comment' => 'Override endpoint',
+            ],
+            'is_builtin' => [
+                'type' => 'BOOLEAN',
+                'default' => true,
+                'comment' => 'False for user-added custom providers',
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addUniqueKey('name');
+        $this->forge->createTable('ai_providers');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('ai_providers');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000011_CreateUserApiKeysTable.php b/app/Database/Migrations/2025-01-01-000011_CreateUserApiKeysTable.php
new file mode 100644
index 0000000..6d44db5
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000011_CreateUserApiKeysTable.php
@@ -0,0 +1,62 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateUserApiKeysTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'user_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'provider_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'api_key_encrypted' => [
+                'type' => 'TEXT',
+                'null' => false,
+                'comment' => 'Store encrypted API key',
+            ],
+            'label' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => true,
+                'comment' => 'e.g., Work OpenAI Key',
+            ],
+            'is_active' => [
+                'type' => 'BOOLEAN',
+                'default' => true,
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+            'last_used_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addUniqueKey(['user_id', 'provider_id']);
+        $this->forge->addForeignKey('user_id', 'users', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->addForeignKey('provider_id', 'ai_providers', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->createTable('user_api_keys');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('user_api_keys');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000012_CreateUserAiSettingsTable.php b/app/Database/Migrations/2025-01-01-000012_CreateUserAiSettingsTable.php
new file mode 100644
index 0000000..548e382
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000012_CreateUserAiSettingsTable.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateUserAiSettingsTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'user_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'default_provider_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => true,
+            ],
+            'default_model' => [
+                'type' => 'VARCHAR',
+                'constraint' => 100,
+                'null' => true,
+                'comment' => 'e.g., gpt-4, claude-3-opus',
+            ],
+            'max_tokens' => [
+                'type' => 'INT',
+                'constraint' => 11,
+                'default' => 2048,
+            ],
+            'temperature' => [
+                'type' => 'FLOAT',
+                'default' => 0.7,
+            ],
+            'updated_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addPrimaryKey('user_id');
+        $this->forge->addForeignKey('user_id', 'users', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->addForeignKey('default_provider_id', 'ai_providers', 'id', 'SET NULL', 'CASCADE');
+        $this->forge->createTable('user_ai_settings');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('user_ai_settings');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000013_CreateAiChatsTable.php b/app/Database/Migrations/2025-01-01-000013_CreateAiChatsTable.php
new file mode 100644
index 0000000..d4b6efb
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000013_CreateAiChatsTable.php
@@ -0,0 +1,65 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateAiChatsTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'user_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'title' => [
+                'type' => 'VARCHAR',
+                'constraint' => 255,
+                'null' => true,
+                'comment' => 'Generated from first message or user-set',
+            ],
+            'provider_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => true,
+            ],
+            'model_used' => [
+                'type' => 'VARCHAR',
+                'constraint' => 100,
+                'null' => true,
+                'comment' => 'Snapshot of model at chat creation',
+            ],
+            'system_prompt' => [
+                'type' => 'TEXT',
+                'null' => true,
+                'comment' => 'Optional custom system prompt for this chat',
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+            'updated_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addKey('user_id');
+        $this->forge->addKey('updated_at');
+        $this->forge->addForeignKey('user_id', 'users', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->addForeignKey('provider_id', 'ai_providers', 'id', 'SET NULL', 'CASCADE');
+        $this->forge->createTable('ai_chats');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('ai_chats');
+    }
+}
diff --git a/app/Database/Migrations/2025-01-01-000014_CreateAiMessagesTable.php b/app/Database/Migrations/2025-01-01-000014_CreateAiMessagesTable.php
new file mode 100644
index 0000000..2582532
--- /dev/null
+++ b/app/Database/Migrations/2025-01-01-000014_CreateAiMessagesTable.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace App\Database\Migrations;
+
+use CodeIgniter\Database\Migration;
+
+class CreateAiMessagesTable extends Migration
+{
+    public function up()
+    {
+        $this->forge->addField([
+            'id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'chat_id' => [
+                'type' => 'CHAR',
+                'constraint' => 36,
+                'null' => false,
+            ],
+            'role' => [
+                'type' => 'ENUM',
+                'constraint' => ['user', 'assistant', 'system'],
+                'null' => false,
+            ],
+            'content' => [
+                'type' => 'TEXT',
+                'null' => false,
+            ],
+            'tokens_used' => [
+                'type' => 'INT',
+                'constraint' => 11,
+                'null' => true,
+                'comment' => 'Optional token count for billing/analysis',
+            ],
+            'created_at' => [
+                'type' => 'DATETIME',
+                'null' => true,
+            ],
+        ]);
+        $this->forge->addKey('id', true);
+        $this->forge->addKey('chat_id');
+        $this->forge->addForeignKey('chat_id', 'ai_chats', 'id', 'CASCADE', 'CASCADE');
+        $this->forge->createTable('ai_messages');
+    }
+
+    public function down()
+    {
+        $this->forge->dropTable('ai_messages');
+    }
+}
diff --git a/app/Database/Seeds/AiProvidersSeeder.php b/app/Database/Seeds/AiProvidersSeeder.php
new file mode 100644
index 0000000..eb64ac2
--- /dev/null
+++ b/app/Database/Seeds/AiProvidersSeeder.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace App\Database\Seeds;
+
+use CodeIgniter\Database\Seeder;
+
+class AiProvidersSeeder extends Seeder
+{
+    public function run()
+    {
+        $data = [
+            [
+                'id' => '550e8400-e29b-41d4-a716-446655440001',
+                'name' => 'openai',
+                'display_name' => 'OpenAI',
+                'base_url' => 'https://api.openai.com/v1',
+                'is_builtin' => true,
+                'created_at' => date('Y-m-d H:i:s'),
+            ],
+            [
+                'id' => '550e8400-e29b-41d4-a716-446655440002',
+                'name' => 'anthropic',
+                'display_name' => 'Anthropic',
+                'base_url' => 'https://api.anthropic.com',
+                'is_builtin' => true,
+                'created_at' => date('Y-m-d H:i:s'),
+            ],
+            [
+                'id' => '550e8400-e29b-41d4-a716-446655440003',
+                'name' => 'google',
+                'display_name' => 'Google AI',
+                'base_url' => 'https://generativelanguage.googleapis.com/v1',
+                'is_builtin' => true,
+                'created_at' => date('Y-m-d H:i:s'),
+            ],
+        ];
+
+        $this->db->table('ai_providers')->insertBatch($data);
+    }
+}
diff --git a/app/Database/Seeds/MarketplaceThemesSeeder.php b/app/Database/Seeds/MarketplaceThemesSeeder.php
new file mode 100644
index 0000000..9d26bc3
--- /dev/null
+++ b/app/Database/Seeds/MarketplaceThemesSeeder.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace App\Database\Seeds;
+
+use CodeIgniter\Database\Seeder;
+
+class MarketplaceThemesSeeder extends Seeder
+{
+    public function run()
+    {
+        $data = [
+            [
+                'id' => '550e8400-e29b-41d4-a716-446655440010',
+                'name' => 'default-light',
+                'display_name' => 'Default Light',
+                'description' => 'Clean and simple light theme',
+                'author' => 'System',
+                'version' => '1.0.0',
+                'thumbnail_url' => null,
+                'download_url' => '/themes/default-light.zip',
+                'price' => 0,
+                'is_published' => true,
+                'metadata' => json_encode(['tags' => ['light', 'clean']]),
+                'created_at' => date('Y-m-d H:i:s'),
+                'updated_at' => date('Y-m-d H:i:s'),
+            ],
+            [
+                'id' => '550e8400-e29b-41d4-a716-446655440011',
+                'name' => 'default-dark',
+                'display_name' => 'Default Dark',
+                'description' => 'Dark theme for night owls',
+                'author' => 'System',
+                'version' => '1.0.0',
+                'thumbnail_url' => null,
+                'download_url' => '/themes/default-dark.zip',
+                'price' => 0,
+                'is_published' => true,
+                'metadata' => json_encode(['tags' => ['dark', 'night']]),
+                'created_at' => date('Y-m-d H:i:s'),
+                'updated_at' => date('Y-m-d H:i:s'),
+            ],
+        ];
+
+        $this->db->table('marketplace_themes')->insertBatch($data);
+    }
+}
diff --git a/app/Database/Seeds/SampleDataSeeder.php b/app/Database/Seeds/SampleDataSeeder.php
new file mode 100644
index 0000000..ec9aef2
--- /dev/null
+++ b/app/Database/Seeds/SampleDataSeeder.php
@@ -0,0 +1,313 @@
+<?php
+
+namespace App\Database\Seeds;
+
+use CodeIgniter\Database\Seeder;
+
+class SampleDataSeeder extends Seeder
+{
+    public function run()
+    {
+        // Generate a UUID helper function
+        $generateUuid = function() {
+            return sprintf(
+                '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
+                mt_rand(0, 0xffff), mt_rand(0, 0xffff),
+                mt_rand(0, 0xffff),
+                mt_rand(0, 0x0fff) | 0x4000,
+                mt_rand(0, 0x3fff) | 0x8000,
+                mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
+            );
+        };
+
+        // Create a sample user (or get existing one)
+        $existingUser = $this->db->table('users')->where('email', 'demo@example.com')->get()->getRowArray();
+        if ($existingUser) {
+            $userId = $existingUser['id'];
+        } else {
+            $userId = $generateUuid();
+            $this->db->table('users')->insert([
+                'id' => $userId,
+                'email' => 'demo@example.com',
+                'password_hash' => password_hash('password123', PASSWORD_DEFAULT),
+                'name' => 'Demo User',
+                'avatar_url' => null,
+                'settings' => json_encode(['language' => 'en', 'default_view' => 'list']),
+                'created_at' => date('Y-m-d H:i:s'),
+                'updated_at' => date('Y-m-d H:i:s'),
+            ]);
+        }
+
+        // Create sample categories (check for existing)
+        $existingCategories = $this->db->table('categories')->where('user_id', $userId)->get()->getResultArray();
+        $existingCategoryNames = array_column($existingCategories, 'name');
+
+        $categories = [];
+        $categoryNames = ['Work', 'Home', 'Personal'];
+        $categoryColors = ['#3B82F6', '#10B981', '#F59E0B'];
+        $categoryFavorites = [true, false, false];
+
+        foreach ($categoryNames as $index => $name) {
+            if (!in_array($name, $existingCategoryNames)) {
+                $categories[] = [
+                    'id' => $generateUuid(),
+                    'user_id' => $userId,
+                    'name' => $name,
+                    'color' => $categoryColors[$index],
+                    'favorite' => $categoryFavorites[$index],
+                    'created_at' => date('Y-m-d H:i:s'),
+                ];
+            }
+        }
+
+        if (!empty($categories)) {
+            $this->db->table('categories')->insertBatch($categories);
+        }
+
+        // Get all categories for the user (existing + newly created)
+        $allCategories = $this->db->table('categories')->where('user_id', $userId)->get()->getResultArray();
+        $categories = [];
+        foreach ($categoryNames as $name) {
+            foreach ($allCategories as $cat) {
+                if ($cat['name'] === $name) {
+                    $categories[] = $cat;
+                    break;
+                }
+            }
+        }
+
+        // Create sample projects (check for existing)
+        $existingProjects = $this->db->table('projects')->where('user_id', $userId)->get()->getResultArray();
+        $existingProjectNames = array_column($existingProjects, 'name');
+
+        $projects = [];
+        $projectData = [
+            ['name' => 'Web Redesign', 'description' => 'Redesign the company website', 'color' => '#8B5CF6'],
+            ['name' => 'Home Renovation', 'description' => 'Renovate the kitchen and bathroom', 'color' => '#EC4899'],
+            ['name' => 'Learning', 'description' => 'Learn new technologies and skills', 'color' => '#14B8A6'],
+        ];
+
+        foreach ($projectData as $proj) {
+            if (!in_array($proj['name'], $existingProjectNames)) {
+                $projects[] = [
+                    'id' => $generateUuid(),
+                    'user_id' => $userId,
+                    'name' => $proj['name'],
+                    'description' => $proj['description'],
+                    'color' => $proj['color'],
+                    'created_at' => date('Y-m-d H:i:s'),
+                ];
+            }
+        }
+
+        if (!empty($projects)) {
+            $this->db->table('projects')->insertBatch($projects);
+        }
+
+        // Get all projects for the user
+        $allProjects = $this->db->table('projects')->where('user_id', $userId)->get()->getResultArray();
+        $projects = [];
+        foreach ($projectData as $proj) {
+            foreach ($allProjects as $p) {
+                if ($p['name'] === $proj['name']) {
+                    $projects[] = $p;
+                    break;
+                }
+            }
+        }
+
+        $webRedesignId = isset($projects[0]) ? $projects[0]['id'] : null;
+        $homeRenovationId = isset($projects[1]) ? $projects[1]['id'] : null;
+        $learningId = isset($projects[2]) ? $projects[2]['id'] : null;
+
+        // Create sample todos (check for existing)
+        $existingTodos = $this->db->table('todos')->where('user_id', $userId)->get()->getResultArray();
+        $existingTodoTitles = array_column($existingTodos, 'title');
+
+        $todos = [];
+        $todoData = [
+            [
+                'title' => 'Bestehende Aufgaben analysieren',
+                'description' => 'Aktuellen Aufbau der Todo-App sichten und Felder abstimmen.',
+                'status' => 'open',
+                'due_date' => date('Y-m-d', strtotime('+7 days')),
+                'due_time' => '10:30:00',
+                'sync_enabled' => true,
+                'reminder_enabled' => false,
+                'recurring_enabled' => false,
+                'project_id' => $webRedesignId,
+            ],
+            [
+                'title' => 'Wireframes erstellen',
+                'description' => 'Erste Skizzen für das neue Design machen.',
+                'status' => 'in_progress',
+                'due_date' => date('Y-m-d', strtotime('+14 days')),
+                'sync_enabled' => true,
+                'reminder_enabled' => true,
+                'recurring_enabled' => false,
+                'project_id' => $webRedesignId,
+            ],
+            [
+                'title' => 'Küche planen',
+                'description' => 'Neue Küche auswählen und bestellen.',
+                'status' => 'open',
+                'due_date' => date('Y-m-d', strtotime('+30 days')),
+                'sync_enabled' => false,
+                'reminder_enabled' => true,
+                'recurring_enabled' => false,
+                'project_id' => $homeRenovationId,
+            ],
+            [
+                'title' => 'CodeIgniter lernen',
+                'description' => 'Offizielle Dokumentation durchgehen.',
+                'status' => 'completed',
+                'due_date' => date('Y-m-d', strtotime('-5 days')),
+                'sync_enabled' => true,
+                'reminder_enabled' => false,
+                'recurring_enabled' => false,
+                'project_id' => $learningId,
+            ],
+            [
+                'title' => 'Einkaufen',
+                'description' => 'Milch, Brot, Eier, Gemüse',
+                'status' => 'open',
+                'due_date' => date('Y-m-d', strtotime('+1 day')),
+                'sync_enabled' => true,
+                'reminder_enabled' => true,
+                'recurring_enabled' => false,
+                'project_id' => null,
+            ],
+        ];
+
+        foreach ($todoData as $todo) {
+            if (!in_array($todo['title'], $existingTodoTitles)) {
+                $todos[] = array_merge($todo, [
+                    'id' => $generateUuid(),
+                    'user_id' => $userId,
+                    'created_at' => date('Y-m-d H:i:s'),
+                    'updated_at' => date('Y-m-d H:i:s'),
+                ]);
+            }
+        }
+
+        if (!empty($todos)) {
+            $this->db->table('todos')->insertBatch($todos);
+        }
+
+        // Get all todos for the user
+        $allTodos = $this->db->table('todos')->where('user_id', $userId)->get()->getResultArray();
+
+        // Link todos to categories
+        $workCategoryId = $categories[0]['id'];
+        $homeCategoryId = $categories[1]['id'];
+        $personalCategoryId = $categories[2]['id'];
+
+        $todoCategories = [];
+        $todoCategoryMap = [
+            'Bestehende Aufgaben analysieren' => $workCategoryId,
+            'Wireframes erstellen' => $workCategoryId,
+            'Küche planen' => $homeCategoryId,
+            'CodeIgniter lernen' => $workCategoryId,
+            'Einkaufen' => $personalCategoryId,
+        ];
+
+        foreach ($allTodos as $todo) {
+            if (isset($todoCategoryMap[$todo['title']])) {
+                // Check if this link already exists
+                $existingLink = $this->db->table('todo_categories')
+                    ->where('todo_id', $todo['id'])
+                    ->where('category_id', $todoCategoryMap[$todo['title']])
+                    ->get()
+                    ->getRowArray();
+
+                if (!$existingLink) {
+                    $todoCategories[] = [
+                        'todo_id' => $todo['id'],
+                        'category_id' => $todoCategoryMap[$todo['title']],
+                    ];
+                }
+            }
+        }
+
+        if (!empty($todoCategories)) {
+            $this->db->table('todo_categories')->insertBatch($todoCategories);
+        }
+
+        // Create sample recurring tasks (check for existing)
+        $existingRecurringTasks = $this->db->table('recurring_tasks')->where('user_id', $userId)->get()->getResultArray();
+        $existingRecurringTaskTitles = array_column($existingRecurringTasks, 'title');
+
+        $recurringTasks = [];
+        $recurringTaskData = [
+            [
+                'title' => 'Weekly review',
+                'description' => 'Plan next week\'s tasks',
+                'schedule' => 'weekly',
+                'custom_days' => json_encode([]),
+                'favorite' => true,
+            ],
+            [
+                'title' => 'Clean the house',
+                'description' => 'Every Saturday',
+                'schedule' => 'custom',
+                'custom_days' => json_encode(['sat']),
+                'favorite' => false,
+            ],
+            [
+                'title' => 'Daily standup',
+                'description' => 'Team meeting every morning',
+                'schedule' => 'daily',
+                'custom_days' => json_encode([]),
+                'favorite' => true,
+            ],
+        ];
+
+        foreach ($recurringTaskData as $task) {
+            if (!in_array($task['title'], $existingRecurringTaskTitles)) {
+                $recurringTasks[] = array_merge($task, [
+                    'id' => $generateUuid(),
+                    'user_id' => $userId,
+                    'created_at' => date('Y-m-d H:i:s'),
+                    'updated_at' => date('Y-m-d H:i:s'),
+                ]);
+            }
+        }
+
+        if (!empty($recurringTasks)) {
+            $this->db->table('recurring_tasks')->insertBatch($recurringTasks);
+        }
+
+        // Get all recurring tasks for the user
+        $allRecurringTasks = $this->db->table('recurring_tasks')->where('user_id', $userId)->get()->getResultArray();
+
+        // Link recurring tasks to categories
+        $recurringTaskCategories = [];
+        $recurringTaskCategoryMap = [
+            'Weekly review' => $workCategoryId,
+            'Clean the house' => $homeCategoryId,
+            'Daily standup' => $workCategoryId,
+        ];
+
+        foreach ($allRecurringTasks as $task) {
+            if (isset($recurringTaskCategoryMap[$task['title']])) {
+                // Check if this link already exists
+                $existingLink = $this->db->table('recurring_task_categories')
+                    ->where('recurring_task_id', $task['id'])
+                    ->where('category_id', $recurringTaskCategoryMap[$task['title']])
+                    ->get()
+                    ->getRowArray();
+
+                if (!$existingLink) {
+                    $recurringTaskCategories[] = [
+                        'recurring_task_id' => $task['id'],
+                        'category_id' => $recurringTaskCategoryMap[$task['title']],
+                    ];
+                }
+            }
+        }
+
+        if (!empty($recurringTaskCategories)) {
+            $this->db->table('recurring_task_categories')->insertBatch($recurringTaskCategories);
+        }
+    }
+}
diff --git a/app/Models/ActivityLogModel.php b/app/Models/ActivityLogModel.php
new file mode 100644
index 0000000..1b9bc09
--- /dev/null
+++ b/app/Models/ActivityLogModel.php
@@ -0,0 +1,97 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class ActivityLogModel extends Model
+{
+    protected $table = 'activity_logs';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'user_id',
+        'action',
+        'entity_type',
+        'entity_id',
+        'details',
+        'ip_address',
+        'user_agent',
+        'created_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = null;
+
+    protected $validationRules = [
+        'action' => 'required|max_length[255]',
+    ];
+
+    // Log an activity
+    public function logActivity($data)
+    {
+        // Disable events to prevent any recursive logging
+        $this->skipEvents();
+
+        if (!isset($data['id'])) {
+            $data['id'] = $this->generateUuid();
+        }
+        if (!isset($data['created_at'])) {
+            $data['created_at'] = date('Y-m-d H:i:s');
+        }
+
+        $result = $this->insert($data);
+
+        // Re-enable events
+        $this->skipEvents(false);
+
+        return $result;
+    }
+
+    // Get logs by user
+    public function getByUser($userId, $limit = 50)
+    {
+        return $this->where('user_id', $userId)
+                    ->orderBy('created_at', 'DESC')
+                    ->limit($limit)
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Get logs by entity
+    public function getByEntity($entityType, $entityId, $limit = 50)
+    {
+        return $this->where('entity_type', $entityType)
+                    ->where('entity_id', $entityId)
+                    ->orderBy('created_at', 'DESC')
+                    ->limit($limit)
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Get logs by action
+    public function getByAction($action, $limit = 50)
+    {
+        return $this->where('action', $action)
+                    ->orderBy('created_at', 'DESC')
+                    ->limit($limit)
+                    ->get()
+                    ->getResultArray();
+    }
+
+    private function generateUuid()
+    {
+        return sprintf(
+            '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff),
+            mt_rand(0, 0xffff),
+            mt_rand(0, 0x0fff) | 0x4000,
+            mt_rand(0, 0x3fff) | 0x8000,
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
+        );
+    }
+}
diff --git a/app/Models/AiChatModel.php b/app/Models/AiChatModel.php
new file mode 100644
index 0000000..143a612
--- /dev/null
+++ b/app/Models/AiChatModel.php
@@ -0,0 +1,105 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class AiChatModel extends Model
+{
+    protected $table = 'ai_chats';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'user_id',
+        'title',
+        'provider_id',
+        'model_used',
+        'system_prompt',
+        'created_at',
+        'updated_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = 'updated_at';
+
+    protected $validationRules = [
+        'user_id' => 'required',
+    ];
+
+    // Get chats by user
+    public function getByUser($userId, $limit = 50)
+    {
+        return $this->where('user_id', $userId)
+                    ->orderBy('updated_at', 'DESC')
+                    ->limit($limit)
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Get chat with message count
+    public function getWithMessageCount($chatId)
+    {
+        $chat = $this->find($chatId);
+        if ($chat) {
+            $messageModel = new AiMessageModel();
+            $chat['message_count'] = $messageModel->where('chat_id', $chatId)->countAllResults();
+        }
+        return $chat;
+    }
+
+    // Get all chats by user with message counts
+    public function getByUserWithMessageCounts($userId)
+    {
+        $chats = $this->getByUser($userId);
+        $messageModel = new AiMessageModel();
+
+        foreach ($chats as &$chat) {
+            $chat['message_count'] = $messageModel->where('chat_id', $chat['id'])->countAllResults();
+        }
+
+        return $chats;
+    }
+
+    // Get chat with provider info
+    public function getWithProvider($chatId)
+    {
+        return $this->select('ai_chats.*, ai_providers.name as provider_name, ai_providers.display_name')
+                    ->join('ai_providers', 'ai_chats.provider_id = ai_providers.id', 'left')
+                    ->where('ai_chats.id', $chatId)
+                    ->get()
+                    ->getRowArray();
+    }
+
+    // Update chat title
+    public function updateTitle($chatId, $title)
+    {
+        return $this->update($chatId, ['title' => $title]);
+    }
+
+    // Create new chat
+    public function createChat($userId, $data = [])
+    {
+        $data['id'] = $this->generateUuid();
+        $data['user_id'] = $userId;
+        $data['created_at'] = date('Y-m-d H:i:s');
+        $data['updated_at'] = date('Y-m-d H:i:s');
+
+        return $this->insert($data);
+    }
+
+    private function generateUuid()
+    {
+        return sprintf(
+            '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff),
+            mt_rand(0, 0xffff),
+            mt_rand(0, 0x0fff) | 0x4000,
+            mt_rand(0, 0x3fff) | 0x8000,
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
+        );
+    }
+}
diff --git a/app/Models/AiMessageModel.php b/app/Models/AiMessageModel.php
new file mode 100644
index 0000000..1871407
--- /dev/null
+++ b/app/Models/AiMessageModel.php
@@ -0,0 +1,93 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class AiMessageModel extends Model
+{
+    protected $table = 'ai_messages';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'chat_id',
+        'role',
+        'content',
+        'tokens_used',
+        'created_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = null;
+
+    protected $validationRules = [
+        'chat_id' => 'required',
+        'role' => 'required|in_list[user,assistant,system]',
+        'content' => 'required',
+    ];
+
+    // Get messages by chat
+    public function getByChat($chatId)
+    {
+        return $this->where('chat_id', $chatId)
+                    ->orderBy('created_at', 'ASC')
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Add message to chat
+    public function addMessage($chatId, $role, $content, $tokensUsed = null)
+    {
+        return $this->insert([
+            'id' => $this->generateUuid(),
+            'chat_id' => $chatId,
+            'role' => $role,
+            'content' => $content,
+            'tokens_used' => $tokensUsed,
+            'created_at' => date('Y-m-d H:i:s'),
+        ]);
+    }
+
+    // Get last message from chat
+    public function getLastMessage($chatId)
+    {
+        return $this->where('chat_id', $chatId)
+                    ->orderBy('created_at', 'DESC')
+                    ->limit(1)
+                    ->get()
+                    ->getRowArray();
+    }
+
+    // Delete all messages from chat
+    public function deleteByChat($chatId)
+    {
+        return $this->where('chat_id', $chatId)->delete();
+    }
+
+    // Get total tokens used by chat
+    public function getTotalTokens($chatId)
+    {
+        $result = $this->selectSum('tokens_used')
+                       ->where('chat_id', $chatId)
+                       ->get()
+                       ->getRowArray();
+
+        return $result ? (int) $result['tokens_used'] : 0;
+    }
+
+    private function generateUuid()
+    {
+        return sprintf(
+            '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff),
+            mt_rand(0, 0xffff),
+            mt_rand(0, 0x0fff) | 0x4000,
+            mt_rand(0, 0x3fff) | 0x8000,
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
+        );
+    }
+}
diff --git a/app/Models/AiProviderModel.php b/app/Models/AiProviderModel.php
new file mode 100644
index 0000000..ce0a587
--- /dev/null
+++ b/app/Models/AiProviderModel.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class AiProviderModel extends Model
+{
+    protected $table = 'ai_providers';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'name',
+        'display_name',
+        'base_url',
+        'is_builtin',
+        'created_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = null;
+
+    protected $validationRules = [
+        'name' => 'required|max_length[100]|is_unique[ai_providers.name]',
+        'display_name' => 'required|max_length[255]',
+    ];
+
+    // Get builtin providers only
+    public function getBuiltinProviders()
+    {
+        return $this->where('is_builtin', true)
+                    ->orderBy('name', 'ASC')
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Get custom providers only
+    public function getCustomProviders()
+    {
+        return $this->where('is_builtin', false)
+                    ->orderBy('name', 'ASC')
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Get provider by name
+    public function getByName($name)
+    {
+        return $this->where('name', $name)
+                    ->get()
+                    ->getRowArray();
+    }
+}
diff --git a/app/Models/CategoryModel.php b/app/Models/CategoryModel.php
new file mode 100644
index 0000000..a775a0f
--- /dev/null
+++ b/app/Models/CategoryModel.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class CategoryModel extends Model
+{
+    use LoggableTrait;
+
+    protected $table = 'categories';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'user_id',
+        'name',
+        'color',
+        'favorite',
+        'created_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = null;
+
+    protected $validationRules = [
+        'user_id' => 'required',
+        'name' => 'required|max_length[255]',
+    ];
+
+    protected function getEntityType(): string
+    {
+        return 'category';
+    }
+}
diff --git a/app/Models/LoggableTrait.php b/app/Models/LoggableTrait.php
new file mode 100644
index 0000000..822ff6b
--- /dev/null
+++ b/app/Models/LoggableTrait.php
@@ -0,0 +1,142 @@
+<?php
+
+namespace App\Models;
+
+trait LoggableTrait
+{
+    /**
+     * Log activity after insert
+     */
+    protected function afterInsert(array $data)
+    {
+        try {
+            $this->logActivity('created', $data);
+        } catch (\Exception $e) {
+            // Silently fail to avoid breaking the main operation
+            log_message('error', 'Failed to log activity: ' . $e->getMessage());
+        }
+        return $data;
+    }
+
+    /**
+     * Log activity after update
+     */
+    protected function afterUpdate(array $data)
+    {
+        try {
+            $this->logActivity('updated', $data);
+        } catch (\Exception $e) {
+            log_message('error', 'Failed to log activity: ' . $e->getMessage());
+        }
+        return $data;
+    }
+
+    /**
+     * Log activity after delete
+     */
+    protected function afterDelete(array $data)
+    {
+        try {
+            $this->logActivity('deleted', $data);
+        } catch (\Exception $e) {
+            log_message('error', 'Failed to log activity: ' . $e->getMessage());
+        }
+        return $data;
+    }
+
+    /**
+     * Log activity to activity_logs table
+     */
+    protected function logActivity($action, $data)
+    {
+        $activityLogModel = new ActivityLogModel();
+
+        $entityType = $this->getEntityType();
+        $entityId = $data['id'] ?? $data[$this->primaryKey] ?? null;
+        $userId = $data['user_id'] ?? null;
+
+        // Try to get user from session if not in data
+        if ($userId === null && function_exists('session')) {
+            $userId = session()->get('user_id');
+        }
+
+        $logData = [
+            'user_id' => $userId,
+            'action' => $this->getActionName($action, $entityType),
+            'entity_type' => $entityType,
+            'entity_id' => $entityId,
+            'details' => json_encode($this->getLogDetails($action, $data)),
+            'ip_address' => $this->getClientIp(),
+            'user_agent' => $this->getUserAgent(),
+        ];
+
+        $activityLogModel->logActivity($logData);
+    }
+
+    /**
+     * Get entity type based on table name
+     */
+    protected function getEntityType(): string
+    {
+        $table = $this->table;
+        // Remove plural 's' if present
+        return rtrim($table, 's');
+    }
+
+    /**
+     * Get formatted action name
+     */
+    protected function getActionName($action, $entityType): string
+    {
+        return "{$entityType}_{$action}";
+    }
+
+    /**
+     * Get log details (can be overridden in models)
+     */
+    protected function getLogDetails($action, $data): array
+    {
+        $details = [
+            'action' => $action,
+        ];
+
+        // Add relevant fields based on entity type
+        if (isset($data['title'])) {
+            $details['title'] = $data['title'];
+        }
+        if (isset($data['name'])) {
+            $details['name'] = $data['name'];
+        }
+        if (isset($data['email'])) {
+            $details['email'] = $data['email'];
+        }
+
+        return $details;
+    }
+
+    /**
+     * Get client IP address
+     */
+    protected function getClientIp(): ?string
+    {
+        try {
+            $request = \Config\Services::request();
+            return $request->getIPAddress();
+        } catch (\Exception $e) {
+            return 'CLI';
+        }
+    }
+
+    /**
+     * Get user agent
+     */
+    protected function getUserAgent(): ?string
+    {
+        try {
+            $request = \Config\Services::request();
+            return $request->getUserAgent()->toString();
+        } catch (\Exception $e) {
+            return 'CLI/Script';
+        }
+    }
+}
diff --git a/app/Models/MarketplaceThemeModel.php b/app/Models/MarketplaceThemeModel.php
new file mode 100644
index 0000000..453660b
--- /dev/null
+++ b/app/Models/MarketplaceThemeModel.php
@@ -0,0 +1,68 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class MarketplaceThemeModel extends Model
+{
+    protected $table = 'marketplace_themes';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'name',
+        'display_name',
+        'description',
+        'author',
+        'version',
+        'thumbnail_url',
+        'download_url',
+        'price',
+        'is_published',
+        'metadata',
+        'created_at',
+        'updated_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = 'updated_at';
+
+    protected $validationRules = [
+        'name' => 'required|max_length[255]|is_unique[marketplace_themes.name]',
+        'display_name' => 'required|max_length[255]',
+        'download_url' => 'required',
+    ];
+
+    // Get published themes only
+    public function getPublished()
+    {
+        return $this->where('is_published', true)
+                    ->orderBy('created_at', 'DESC')
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Get free themes
+    public function getFreeThemes()
+    {
+        return $this->where('price', 0)
+                    ->where('is_published', true)
+                    ->orderBy('created_at', 'DESC')
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Get paid themes
+    public function getPaidThemes()
+    {
+        return $this->where('price >', 0)
+                    ->where('is_published', true)
+                    ->orderBy('price', 'ASC')
+                    ->get()
+                    ->getResultArray();
+    }
+}
diff --git a/app/Models/ProjectModel.php b/app/Models/ProjectModel.php
new file mode 100644
index 0000000..c5691f7
--- /dev/null
+++ b/app/Models/ProjectModel.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class ProjectModel extends Model
+{
+    use LoggableTrait;
+
+    protected $table = 'projects';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'user_id',
+        'name',
+        'description',
+        'color',
+        'created_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = null;
+
+    protected $validationRules = [
+        'user_id' => 'required',
+        'name' => 'required|max_length[255]',
+    ];
+
+    protected function getEntityType(): string
+    {
+        return 'project';
+    }
+}
diff --git a/app/Models/RecurringTaskCategoryModel.php b/app/Models/RecurringTaskCategoryModel.php
new file mode 100644
index 0000000..0dcf094
--- /dev/null
+++ b/app/Models/RecurringTaskCategoryModel.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class RecurringTaskCategoryModel extends Model
+{
+    protected $table = 'recurring_task_categories';
+    protected $primaryKey = 'recurring_task_id'; // Composite primary key
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'recurring_task_id',
+        'category_id',
+    ];
+
+    protected $useTimestamps = false;
+
+    // Add category to recurring task
+    public function addCategoryToTask($taskId, $categoryId)
+    {
+        return $this->insert([
+            'recurring_task_id' => $taskId,
+            'category_id' => $categoryId,
+        ]);
+    }
+
+    // Remove category from recurring task
+    public function removeCategoryFromTask($taskId, $categoryId)
+    {
+        return $this->where('recurring_task_id', $taskId)
+                    ->where('category_id', $categoryId)
+                    ->delete();
+    }
+
+    // Get categories for a recurring task
+    public function getCategoriesForTask($taskId)
+    {
+        return $this->select('categories.*')
+                    ->join('categories', 'recurring_task_categories.category_id = categories.id')
+                    ->where('recurring_task_categories.recurring_task_id', $taskId)
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Get recurring tasks for a category
+    public function getTasksForCategory($categoryId)
+    {
+        return $this->select('recurring_tasks.*')
+                    ->join('recurring_tasks', 'recurring_task_categories.recurring_task_id = recurring_tasks.id')
+                    ->where('recurring_task_categories.category_id', $categoryId)
+                    ->get()
+                    ->getResultArray();
+    }
+}
diff --git a/app/Models/RecurringTaskModel.php b/app/Models/RecurringTaskModel.php
new file mode 100644
index 0000000..945073d
--- /dev/null
+++ b/app/Models/RecurringTaskModel.php
@@ -0,0 +1,69 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class RecurringTaskModel extends Model
+{
+    use LoggableTrait;
+
+    protected $table = 'recurring_tasks';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'user_id',
+        'title',
+        'description',
+        'schedule',
+        'custom_days',
+        'favorite',
+        'created_at',
+        'updated_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = 'updated_at';
+
+    protected $validationRules = [
+        'user_id' => 'required',
+        'title' => 'required|max_length[255]',
+        'schedule' => 'required|in_list[daily,weekly,monthly,custom]',
+    ];
+
+    protected function getEntityType(): string
+    {
+        return 'recurring_task';
+    }
+
+    // Get recurring tasks with categories
+    public function getWithCategories($taskId = null)
+    {
+        $builder = $this->select('recurring_tasks.*, GROUP_CONCAT(categories.name) as category_names')
+                        ->join('recurring_task_categories', 'recurring_tasks.id = recurring_task_categories.recurring_task_id', 'left')
+                        ->join('categories', 'recurring_task_categories.category_id = categories.id', 'left')
+                        ->groupBy('recurring_tasks.id');
+
+        if ($taskId) {
+            $builder->where('recurring_tasks.id', $taskId);
+        }
+
+        return $builder->get()->getResultArray();
+    }
+
+    // Get recurring tasks by user with categories
+    public function getByUserWithCategories($userId)
+    {
+        return $this->select('recurring_tasks.*, GROUP_CONCAT(categories.name) as category_names')
+                    ->join('recurring_task_categories', 'recurring_tasks.id = recurring_task_categories.recurring_task_id', 'left')
+                    ->join('categories', 'recurring_task_categories.category_id = categories.id', 'left')
+                    ->where('recurring_tasks.user_id', $userId)
+                    ->groupBy('recurring_tasks.id')
+                    ->get()
+                    ->getResultArray();
+    }
+}
diff --git a/app/Models/TodoCategoryModel.php b/app/Models/TodoCategoryModel.php
new file mode 100644
index 0000000..fc4f56e
--- /dev/null
+++ b/app/Models/TodoCategoryModel.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class TodoCategoryModel extends Model
+{
+    protected $table = 'todo_categories';
+    protected $primaryKey = 'todo_id'; // Composite primary key
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'todo_id',
+        'category_id',
+    ];
+
+    protected $useTimestamps = false;
+
+    // Add category to todo
+    public function addCategoryToTodo($todoId, $categoryId)
+    {
+        return $this->insert([
+            'todo_id' => $todoId,
+            'category_id' => $categoryId,
+        ]);
+    }
+
+    // Remove category from todo
+    public function removeCategoryFromTodo($todoId, $categoryId)
+    {
+        return $this->where('todo_id', $todoId)
+                    ->where('category_id', $categoryId)
+                    ->delete();
+    }
+
+    // Get categories for a todo
+    public function getCategoriesForTodo($todoId)
+    {
+        return $this->select('categories.*')
+                    ->join('categories', 'todo_categories.category_id = categories.id')
+                    ->where('todo_categories.todo_id', $todoId)
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Get todos for a category
+    public function getTodosForCategory($categoryId)
+    {
+        return $this->select('todos.*')
+                    ->join('todos', 'todo_categories.todo_id = todos.id')
+                    ->where('todo_categories.category_id', $categoryId)
+                    ->get()
+                    ->getResultArray();
+    }
+}
diff --git a/app/Models/TodoModel.php b/app/Models/TodoModel.php
new file mode 100644
index 0000000..3a484f4
--- /dev/null
+++ b/app/Models/TodoModel.php
@@ -0,0 +1,73 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class TodoModel extends Model
+{
+    use LoggableTrait;
+
+    protected $table = 'todos';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'user_id',
+        'title',
+        'description',
+        'status',
+        'due_date',
+        'due_time',
+        'sync_enabled',
+        'reminder_enabled',
+        'recurring_enabled',
+        'project_id',
+        'created_at',
+        'updated_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = 'updated_at';
+
+    protected $validationRules = [
+        'user_id' => 'required',
+        'title' => 'required|max_length[255]',
+        'status' => 'permit_empty|in_list[open,in_progress,completed,archived]',
+    ];
+
+    protected function getEntityType(): string
+    {
+        return 'todo';
+    }
+
+    // Get todos with categories
+    public function getWithCategories($todoId = null)
+    {
+        $builder = $this->select('todos.*, GROUP_CONCAT(categories.name) as category_names')
+                        ->join('todo_categories', 'todos.id = todo_categories.todo_id', 'left')
+                        ->join('categories', 'todo_categories.category_id = categories.id', 'left')
+                        ->groupBy('todos.id');
+
+        if ($todoId) {
+            $builder->where('todos.id', $todoId);
+        }
+
+        return $builder->get()->getResultArray();
+    }
+
+    // Get todos by user with categories
+    public function getByUserWithCategories($userId)
+    {
+        return $this->select('todos.*, GROUP_CONCAT(categories.name) as category_names')
+                    ->join('todo_categories', 'todos.id = todo_categories.todo_id', 'left')
+                    ->join('categories', 'todo_categories.category_id = categories.id', 'left')
+                    ->where('todos.user_id', $userId)
+                    ->groupBy('todos.id')
+                    ->get()
+                    ->getResultArray();
+    }
+}
diff --git a/app/Models/UserAiSettingsModel.php b/app/Models/UserAiSettingsModel.php
new file mode 100644
index 0000000..8bca40d
--- /dev/null
+++ b/app/Models/UserAiSettingsModel.php
@@ -0,0 +1,68 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class UserAiSettingsModel extends Model
+{
+    protected $table = 'user_ai_settings';
+    protected $primaryKey = 'user_id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'user_id',
+        'default_provider_id',
+        'default_model',
+        'max_tokens',
+        'temperature',
+        'updated_at',
+    ];
+
+    protected $useTimestamps = false;
+
+    protected $validationRules = [
+        'user_id' => 'required',
+        'max_tokens' => 'permit_empty|integer|greater_than[0]',
+        'temperature' => 'permit_empty|numeric|greater_than_equal_to[0]|less_than_equal_to[2]',
+    ];
+
+    // Get or create settings for user
+    public function getSettings($userId)
+    {
+        $settings = $this->find($userId);
+
+        if (!$settings) {
+            // Create default settings
+            $this->insert([
+                'user_id' => $userId,
+                'default_provider_id' => null,
+                'default_model' => null,
+                'max_tokens' => 2048,
+                'temperature' => 0.7,
+                'updated_at' => date('Y-m-d H:i:s'),
+            ]);
+            $settings = $this->find($userId);
+        }
+
+        return $settings;
+    }
+
+    // Update settings for user
+    public function updateSettings($userId, $data)
+    {
+        $data['updated_at'] = date('Y-m-d H:i:s');
+        return $this->update($userId, $data);
+    }
+
+    // Get settings with provider info
+    public function getSettingsWithProvider($userId)
+    {
+        return $this->select('user_ai_settings.*, ai_providers.name as provider_name, ai_providers.display_name')
+                    ->join('ai_providers', 'user_ai_settings.default_provider_id = ai_providers.id', 'left')
+                    ->where('user_ai_settings.user_id', $userId)
+                    ->get()
+                    ->getRowArray();
+    }
+}
diff --git a/app/Models/UserApiKeyModel.php b/app/Models/UserApiKeyModel.php
new file mode 100644
index 0000000..d2b8fe1
--- /dev/null
+++ b/app/Models/UserApiKeyModel.php
@@ -0,0 +1,108 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class UserApiKeyModel extends Model
+{
+    protected $table = 'user_api_keys';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'user_id',
+        'provider_id',
+        'api_key_encrypted',
+        'label',
+        'is_active',
+        'created_at',
+        'last_used_at',
+    ];
+
+    protected $useTimestamps = false;
+
+    protected $validationRules = [
+        'user_id' => 'required',
+        'provider_id' => 'required',
+        'api_key_encrypted' => 'required',
+    ];
+
+    // Save or update API key for user and provider
+    public function saveApiKey($userId, $providerId, $encryptedKey, $label = null)
+    {
+        $existing = $this->where('user_id', $userId)
+                         ->where('provider_id', $providerId)
+                         ->first();
+
+        if ($existing) {
+            return $this->update($existing['id'], [
+                'api_key_encrypted' => $encryptedKey,
+                'label' => $label,
+                'is_active' => true,
+                'last_used_at' => null,
+            ]);
+        } else {
+            return $this->insert([
+                'id' => $this->generateUuid(),
+                'user_id' => $userId,
+                'provider_id' => $providerId,
+                'api_key_encrypted' => $encryptedKey,
+                'label' => $label,
+                'is_active' => true,
+                'created_at' => date('Y-m-d H:i:s'),
+                'last_used_at' => null,
+            ]);
+        }
+    }
+
+    // Get API key for user and provider
+    public function getApiKey($userId, $providerId)
+    {
+        return $this->where('user_id', $userId)
+                    ->where('provider_id', $providerId)
+                    ->where('is_active', true)
+                    ->first();
+    }
+
+    // Get all API keys for user
+    public function getUserApiKeys($userId)
+    {
+        return $this->select('user_api_keys.*, ai_providers.name as provider_name, ai_providers.display_name')
+                    ->join('ai_providers', 'user_api_keys.provider_id = ai_providers.id')
+                    ->where('user_api_keys.user_id', $userId)
+                    ->orderBy('user_api_keys.created_at', 'DESC')
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Deactivate API key
+    public function deactivateApiKey($userId, $providerId)
+    {
+        return $this->where('user_id', $userId)
+                    ->where('provider_id', $providerId)
+                    ->update(['is_active' => false]);
+    }
+
+    // Update last used timestamp
+    public function updateLastUsed($userId, $providerId)
+    {
+        return $this->where('user_id', $userId)
+                    ->where('provider_id', $providerId)
+                    ->update(['last_used_at' => date('Y-m-d H:i:s')]);
+    }
+
+    private function generateUuid()
+    {
+        return sprintf(
+            '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff),
+            mt_rand(0, 0xffff),
+            mt_rand(0, 0x0fff) | 0x4000,
+            mt_rand(0, 0x3fff) | 0x8000,
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
+        );
+    }
+}
diff --git a/app/Models/UserModel.php b/app/Models/UserModel.php
new file mode 100644
index 0000000..ef1145f
--- /dev/null
+++ b/app/Models/UserModel.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class UserModel extends Model
+{
+    use LoggableTrait;
+
+    protected $table = 'users';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'email',
+        'password_hash',
+        'name',
+        'avatar_url',
+        'settings',
+        'created_at',
+        'updated_at',
+    ];
+
+    protected $useTimestamps = true;
+    protected $createdField = 'created_at';
+    protected $updatedField = 'updated_at';
+
+    protected $validationRules = [
+        'email' => 'required|valid_email|is_unique[users.email]',
+        'password_hash' => 'required',
+    ];
+
+    protected $validationMessages = [
+        'email' => [
+            'required' => 'Email is required',
+            'valid_email' => 'Please enter a valid email address',
+            'is_unique' => 'This email is already registered',
+        ],
+    ];
+
+    protected function getEntityType(): string
+    {
+        return 'user';
+    }
+}
diff --git a/app/Models/UserThemeModel.php b/app/Models/UserThemeModel.php
new file mode 100644
index 0000000..6ee6047
--- /dev/null
+++ b/app/Models/UserThemeModel.php
@@ -0,0 +1,104 @@
+<?php
+
+namespace App\Models;
+
+use CodeIgniter\Model;
+
+class UserThemeModel extends Model
+{
+    protected $table = 'user_themes';
+    protected $primaryKey = 'id';
+    protected $useAutoIncrement = false;
+    protected $returnType = 'array';
+    protected $useSoftDeletes = false;
+    protected $allowedFields = [
+        'id',
+        'user_id',
+        'theme_id',
+        'installed_at',
+        'active',
+        'custom_settings',
+    ];
+
+    protected $useTimestamps = false;
+
+    protected $validationRules = [
+        'user_id' => 'required',
+        'theme_id' => 'required',
+    ];
+
+    // Install theme for user
+    public function installTheme($userId, $themeId)
+    {
+        return $this->insert([
+            'id' => $this->generateUuid(),
+            'user_id' => $userId,
+            'theme_id' => $themeId,
+            'installed_at' => date('Y-m-d H:i:s'),
+            'active' => false,
+            'custom_settings' => json_encode([]),
+        ]);
+    }
+
+    // Uninstall theme for user
+    public function uninstallTheme($userId, $themeId)
+    {
+        return $this->where('user_id', $userId)
+                    ->where('theme_id', $themeId)
+                    ->delete();
+    }
+
+    // Set active theme for user
+    public function setActiveTheme($userId, $themeId)
+    {
+        // Deactivate all themes for user
+        $this->where('user_id', $userId)->update(['active' => false]);
+
+        // Activate the specified theme
+        return $this->where('user_id', $userId)
+                    ->where('theme_id', $themeId)
+                    ->update(['active' => true]);
+    }
+
+    // Get active theme for user
+    public function getActiveTheme($userId)
+    {
+        return $this->select('user_themes.*, marketplace_themes.*')
+                    ->join('marketplace_themes', 'user_themes.theme_id = marketplace_themes.id')
+                    ->where('user_themes.user_id', $userId)
+                    ->where('user_themes.active', true)
+                    ->get()
+                    ->getRowArray();
+    }
+
+    // Get all installed themes for user
+    public function getUserThemes($userId)
+    {
+        return $this->select('user_themes.*, marketplace_themes.*')
+                    ->join('marketplace_themes', 'user_themes.theme_id = marketplace_themes.id')
+                    ->where('user_themes.user_id', $userId)
+                    ->orderBy('user_themes.installed_at', 'DESC')
+                    ->get()
+                    ->getResultArray();
+    }
+
+    // Check if theme is installed for user
+    public function isInstalled($userId, $themeId)
+    {
+        return $this->where('user_id', $userId)
+                    ->where('theme_id', $themeId)
+                    ->countAllResults() > 0;
+    }
+
+    private function generateUuid()
+    {
+        return sprintf(
+            '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff),
+            mt_rand(0, 0xffff),
+            mt_rand(0, 0x0fff) | 0x4000,
+            mt_rand(0, 0x3fff) | 0x8000,
+            mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
+        );
+    }
+}
diff --git a/example.env b/example.env
new file mode 100644
index 0000000..0cdb5b3
--- /dev/null
+++ b/example.env
@@ -0,0 +1,69 @@
+#--------------------------------------------------------------------
+# Example Environment Configuration file
+#
+# This file can be used as a starting point for your own
+# custom .env files, and contains most of the possible settings
+# available in a default install.
+#
+# By default, all of the settings are commented out. If you want
+# to override the setting, you must un-comment it by removing the '#'
+# at the beginning of the line.
+#--------------------------------------------------------------------
+
+#--------------------------------------------------------------------
+# ENVIRONMENT
+#--------------------------------------------------------------------
+
+CI_ENVIRONMENT = development
+
+#--------------------------------------------------------------------
+# APP
+#--------------------------------------------------------------------
+
+# app.baseURL = ''
+# If you have trouble with `.`, you could also use `_`.
+# app_baseURL = ''
+# app.forceGlobalSecureRequests = false
+# app.CSPEnabled = false
+
+#--------------------------------------------------------------------
+# DATABASE
+#--------------------------------------------------------------------
+
+database.default.hostname = 127.0.0.1
+database.default.database = TodoApp
+database.default.username = root
+database.default.password =
+database.default.DBDriver = MySQLi
+# database.default.DBPrefix =
+database.default.port = 3306
+
+# If you use MySQLi as tests, first update the values of Config\Database::$tests.
+# database.tests.hostname = localhost
+# database.tests.database = ci4_test
+# database.tests.username = root
+# database.tests.password = root
+# database.tests.DBDriver = MySQLi
+# database.tests.DBPrefix =
+# database.tests.charset = utf8mb4
+# database.tests.DBCollat = utf8mb4_general_ci
+# database.tests.port = 3306
+
+#--------------------------------------------------------------------
+# ENCRYPTION
+#--------------------------------------------------------------------
+
+# encryption.key =
+
+#--------------------------------------------------------------------
+# SESSION
+#--------------------------------------------------------------------
+
+# session.driver = 'CodeIgniter\Session\Handlers\FileHandler'
+# session.savePath = null
+
+#--------------------------------------------------------------------
+# LOGGER
+#--------------------------------------------------------------------
+
+# logger.threshold = 4