fix: disable library WebSocket keepalive for device server

websockets.serve() defaults to ping_interval=20 and ping_timeout=20.
ESP32 clients that do not answer those pings are dropped with
1011 keepalive ping timeout roughly 40 seconds into a healthy session.
The application-level ping is configured separately via
enable_websocket_ping.

Refs #3348

main/xiaozhi-server/core/websocket_server.py

@@ -74,7 +74,11 @@ class WebSocketServer:
         port = int(server_config.get("port", 8000))
 
         async with websockets.serve(
-            self._handle_connection, host, port, process_request=self._http_response
+            self._handle_connection,
+            host,
+            port,
+            process_request=self._http_response,
+            ping_interval=None,
         ):
             await asyncio.Future()