Fix WS deadlock: start WebSocketManager in thread

frontend/react_gradio_hybrid.py

@@ -2,6 +2,7 @@ import sys
 import json
 import time
 import os
+import asyncio
 from pathlib import Path
 from typing import Dict, List
 import logging
@@ -449,7 +450,7 @@ async def frontend_websocket(websocket: WebSocket, conversation_id: str):
             
             if message_type == "start_conversation":
                 # Start the backend WebSocket manager
-                success = manager.start()
+                success = await asyncio.to_thread(manager.start)
                 
                 if success:
                     # Send start message to backend
@@ -478,7 +479,7 @@ async def frontend_websocket(websocket: WebSocket, conversation_id: str):
                     "content": "stop",
                     "action": "stop"
                 })
-                manager.stop()
+                await asyncio.to_thread(manager.stop)
                 
                 await websocket.send_json({
                     "type": "conversation_status",