fix(admin): isolate login on admin host

Allow runtime request headers through API preflight and keep the storefront shell hidden while admin QR authentication gates backoffice.

src/app/app.ts

@@ -28,6 +28,8 @@ import { TelegramLoginComponent } from './components/telegram-login/telegram-log
 })
 export class App implements OnInit {
   protected title = '';
+  readonly isAdminHost = typeof window !== 'undefined'
+    && window.location.hostname.toLowerCase().startsWith('admin.');
   isHomePage = signal(true);
   isAdminRoute = signal(false);
   checkingServer = signal(true);