fix: serve.py Python 3.8 兼容，asyncio.run 改为手动 event loop

frontend/serve.py

@@ -112,7 +112,10 @@ async def ws_handler(websocket, path):
 
 
 def run_websocket_server():
-    asyncio.run(websockets.serve(ws_handler, "0.0.0.0", PORT))
+    loop = asyncio.new_event_loop()
+    asyncio.set_event_loop(loop)
+    loop.run_until_complete(websockets.serve(ws_handler, "0.0.0.0", PORT))
+    loop.run_forever()
 
 
 if __name__ == "__main__":