implement full backend requirements: pagination, filtering, sorting, meta responses, JWT auth, model validation, request logging, API key management

- BaseController: paginatedResponse() helper with meta (page/perPage/total/lastPage/hasMore), getSortParams(), getFilterParams(), encodeJwt()/decodeJwt(), logActivity() helper, validateWithModel()
- TodoController: paginated/sortable/filterable index, model-based validation, boolean conversion on write, activity logging
- CategoryController: same pagination/sort/filter patterns + duplicate-name check (409)
- ProjectController: paginated index + activity logging
- RecurringTaskController: paginated/sortable/filterable index + junction-table category linking
- AuthController: JWT register/login/refresh endpoints (firebase/php-jwt v7)
- Routes: JWT routes added as public endpoints
- Models: all have proper validationRules with exact error messages (field-level, user-facing)
- ApiAuthFilter: scoped API key auth + UserThemeController generateUuid visibility fix
- composer.json: add firebase/php-jwt ^7.0

app/Models/CategoryModel.php

@@ -6,26 +6,38 @@ use CodeIgniter\Model;
 
 class CategoryModel extends Model
 {
-    protected $table = 'categories';
-    protected $primaryKey = 'id';
+    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 $returnType       = 'array';
+    protected $useSoftDeletes   = false;
+    protected $allowedFields    = [
+        'id', 'user_id', 'name', 'color', 'favorite', 'created_at',
     ];
 
     protected $useTimestamps = true;
-    protected $createdField = 'created_at';
-    protected $updatedField = '';
+    protected $createdField  = 'created_at';
+    protected $updatedField  = '';
 
     protected $validationRules = [
-        'user_id' => 'required',
-        'name' => 'required|max_length[255]',
+        'user_id' => [
+            'rules' => 'required',
+            'errors' => ['required' => 'User ID is required.'],
+        ],
+        'name' => [
+            'rules' => 'required|max_length[255]',
+            'errors' => [
+                'required'   => 'The category name is required.',
+                'max_length' => 'The category name must not exceed 255 characters.',
+            ],
+        ],
+        'color' => [
+            'rules' => 'required|max_length[7]|regex_match[/^#[0-9a-fA-F]{6}$/]',
+            'errors' => [
+                'required'    => 'A color value is required.',
+                'max_length'  => 'Color must be a hex code (e.g. #3B82F6).',
+                'regex_match' => 'Color must be a valid hex code (e.g. #3B82F6).',
+            ],
+        ],
     ];
 }