Add error log management and bulk admin actions

Introduces error log tracking with new ErrorLog model, controller, views, and migration. Adds admin UI for viewing, resolving, and deleting errors. Implements bulk actions for users and notification groups, refactors domain filtering/pagination, and centralizes admin access checks using Auth::requireAdmin().

app/Controllers/SettingsController.php

@@ -3,6 +3,7 @@
 namespace App\Controllers;
 
 use Core\Controller;
+use Core\Auth;
 use App\Models\Setting;
 
 class SettingsController extends Controller
@@ -11,14 +12,8 @@ class SettingsController extends Controller
 
     public function __construct()
     {
+        Auth::requireAdmin();
         $this->settingModel = new Setting();
-        
-        // Ensure only admins can access settings
-        if (!isset($_SESSION['role']) || $_SESSION['role'] !== 'admin') {
-            $_SESSION['error'] = 'Access denied. Admin privileges required.';
-            $this->redirect('/');
-            exit;
-        }
     }
 
     public function index()