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/NotificationGroupController.php

@@ -245,5 +245,41 @@ class NotificationGroupController extends Controller
                 return null;
         }
     }
+
+    /**
+     * Bulk delete notification groups
+     */
+    public function bulkDelete()
+    {
+        if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
+            $this->redirect('/groups');
+            return;
+        }
+
+        $this->verifyCsrf('/groups');
+
+        $groupIdsJson = $_POST['group_ids'] ?? '[]';
+        $groupIds = json_decode($groupIdsJson, true);
+
+        if (empty($groupIds) || !is_array($groupIds)) {
+            $_SESSION['error'] = 'No groups selected for deletion';
+            $this->redirect('/groups');
+            return;
+        }
+
+        $deletedCount = 0;
+
+        foreach ($groupIds as $groupId) {
+            try {
+                $this->groupModel->deleteWithRelations((int)$groupId);
+                $deletedCount++;
+            } catch (\Exception $e) {
+                // Continue with next group
+            }
+        }
+
+        $_SESSION['success'] = "Successfully deleted $deletedCount notification group(s)";
+        $this->redirect('/groups');
+    }
 }