feat: implement NotificationsHub for real-time vault sync notifications

- Added NotificationsHub durable object to handle WebSocket connections for vault sync notifications.
- Integrated SignalR protocol for message framing and communication.
- Updated storage service methods to return revision date and user ID for vault sync notifications.
- Enhanced existing handlers (attachments, ciphers, folders, sends, and import) to notify users of vault sync events.
- Created new notifications handler for WebSocket negotiation and binding user IDs.
- Updated frontend to establish WebSocket connection for receiving vault sync notifications.
- Improved CORS headers to support new notification endpoints.
- Bumped wrangler version in package.json to 4.71.0.

src/index.ts

@@ -1,4 +1,5 @@
 import { Env } from './types';
+import { NotificationsHub } from './durable/notifications-hub';
 import { handleRequest } from './router';
 import { StorageService } from './services/storage';
 import { applyCors, jsonResponse } from './utils/response';
@@ -54,3 +55,5 @@ export default {
     return applyCors(request, resp);
   },
 };
+
+export { NotificationsHub };