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/ApiController.php

@@ -468,17 +468,68 @@ class ApiController
 
     public function appVersion(): void
     {
+        $db = \ServerManager\Core\Database::getInstance();
+        $configs = $db->fetchAll('SELECT * FROM app_config');
+        $config = [];
+        foreach ($configs as $row) {
+            $config[$row['key']] = $row['value'];
+        }
+
         $this->view->json([
             'success' => true,
             'data' => [
-                'version' => '1.0.1',
-                'apk_url' => '/sysadmin.apk',
-                'force_update' => false,
-                'release_notes' => '• Gráficos de métricas en tiempo real\n• Nuevo diseño con animaciones\n• Modo oscuro\n• Perfil de usuario\n• Mejoras de rendimiento',
+                'version' => $config['app_version'] ?? '1.0.0',
+                'apk_url' => $config['apk_url'] ?? '/sysadmin.apk',
+                'force_update' => ($config['force_update'] ?? '0') === '1',
+                'release_notes' => $config['release_notes'] ?? '',
             ],
         ]);
     }
 
+    public function notifications(): void
+    {
+        $user = $this->authenticateRequest();
+
+        $notificationModel = new \ServerManager\Models\Notification();
+        $page = (int) ($_GET['page'] ?? 1);
+        $perPage = (int) ($_GET['per_page'] ?? 20);
+
+        $result = $notificationModel->getForUser((int) $user['id'], $page, $perPage);
+        $unreadCount = $notificationModel->getUnreadCount((int) $user['id']);
+
+        $this->view->json([
+            'success' => true,
+            'data' => $result['data'],
+            'pagination' => [
+                'page' => $result['page'],
+                'per_page' => $result['per_page'],
+                'total' => $result['total'],
+                'total_pages' => $result['total_pages'],
+            ],
+            'unread_count' => $unreadCount,
+        ]);
+    }
+
+    public function markNotificationRead(int $id): void
+    {
+        $user = $this->authenticateRequest();
+
+        $notificationModel = new \ServerManager\Models\Notification();
+        $notificationModel->markAsRead($id, (int) $user['id']);
+
+        $this->view->json(['success' => true]);
+    }
+
+    public function markAllNotificationsRead(): void
+    {
+        $user = $this->authenticateRequest();
+
+        $notificationModel = new \ServerManager\Models\Notification();
+        $notificationModel->markAllAsRead((int) $user['id']);
+
+        $this->view->json(['success' => true]);
+    }
+
     public function login(): void
     {
         $input = json_decode(file_get_contents('php://input'), true) ?? $_POST;