feat: admin app version mgmt + notification system

- New tables: app_config, notifications
- Admin views: App Version editor, Notification sender
- API: GET /api/notifications, POST /api/notifications/:id/read, POST /api/notifications/read-all
- App version now stored in DB, editable by super admin
- Notifications: send to all users or specific user
- Android notification models + API client
- Sidebar: App Version + Notifications links for super_admin

src/Controllers/AdminController.php

@@ -5,8 +5,10 @@ declare(strict_types=1);
 namespace ServerManager\Controllers;
 
 use ServerManager\Core\App;
+use ServerManager\Core\Database;
 use ServerManager\Core\Session;
 use ServerManager\Core\Validator;
+use ServerManager\Models\Notification;
 use ServerManager\Models\User;
 use ServerManager\Services\AuditService;
 
@@ -210,4 +212,79 @@ class AdminController
             'title' => 'Security Settings - ServerManager',
         ]);
     }
+
+    public function appVersion(): void
+    {
+        $this->requireSuperAdmin();
+
+        $db = Database::getInstance();
+
+        if ($_SERVER['REQUEST_METHOD'] === 'POST') {
+            $fields = ['app_version', 'apk_url', 'force_update', 'release_notes'];
+            foreach ($fields as $field) {
+                if (isset($_POST[$field])) {
+                    $db->update('app_config', ['value' => $_POST[$field]], '`key` = ?', [$field]);
+                }
+            }
+            $this->auditService->log('app_version_updated', 'App version config updated');
+            $this->view->json(['success' => true, 'message' => 'App version updated successfully.']);
+            return;
+        }
+
+        $configs = $db->fetchAll('SELECT * FROM app_config');
+        $config = [];
+        foreach ($configs as $row) {
+            $config[$row['key']] = $row['value'];
+        }
+
+        $this->view->display('admin.app_version', [
+            'title' => 'App Version - ServerManager',
+            'config' => $config,
+        ]);
+    }
+
+    public function notifications(): void
+    {
+        $this->requireSuperAdmin();
+
+        $notificationModel = new Notification();
+        $page = (int) ($_GET['page'] ?? 1);
+        $allNotifications = $notificationModel->getAll($page, 20);
+
+        $userModel = new User();
+        $users = $userModel->getAll(1, 200);
+
+        $this->view->display('admin.notifications', [
+            'title' => 'Notifications - ServerManager',
+            'notifications' => $allNotifications,
+            'users' => $users,
+        ]);
+    }
+
+    public function sendNotification(): void
+    {
+        $this->requireSuperAdmin();
+
+        $title = $_POST['title'] ?? '';
+        $message = $_POST['message'] ?? '';
+        $type = $_POST['type'] ?? 'info';
+        $userId = !empty($_POST['user_id']) ? (int) $_POST['user_id'] : null;
+
+        if (empty($title) || empty($message)) {
+            $this->view->json(['success' => false, 'message' => 'Title and message are required.']);
+            return;
+        }
+
+        $notificationModel = new Notification();
+        $notificationModel->create([
+            'user_id' => $userId,
+            'title' => $title,
+            'message' => $message,
+            'type' => $type,
+        ]);
+
+        $this->auditService->log('notification_sent', "Notification: {$title}" . ($userId ? " to user #{$userId}" : ' (all users)'));
+
+        $this->view->json(['success' => true, 'message' => 'Notification sent successfully.']);
+    }
 }