fix: Await response generator in chat completions for proper streaming

src/proxy_app/main.py

@@ -244,7 +244,7 @@ async def chat_completions(
         is_streaming = request_data.get("stream", False)
 
         if is_streaming:
-            response_generator = client.acompletion(request=request, **request_data)
+            response_generator = await client.acompletion(request=request, **request_data)
             return StreamingResponse(
                 streaming_response_wrapper(request, request_data, response_generator),
                 media_type="text/event-stream"