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.

package.json

@@ -43,7 +43,7 @@
     "tsx": "^4.21.0",
     "typescript": "^5.9.3",
     "vite": "^7.3.1",
-    "wrangler": "^4.69.0"
+    "wrangler": "^4.71.0"
   },
   "dependencies": {
     "@noble/hashes": "^2.0.1",