The "prompt" endpoint receives the request with Comfy-User header but never extracts it

### Custom Node Testing

- [x] I have tried disabling custom nodes and the issue persists (see [how to disable custom nodes](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled) if you need help)

### Expected Behavior

The /prompt endpoint at comfyui/server.py:859-909 receives the request with comfy-user header but never extracts it — only client_id is passed to the execution queue.

If any node needs to use that user_id (e.g. to get user-specific settings or user-specific env variable) it's currently not possible.

I managed to fix this by creating an extension that adds Comfy-User header data to "extra_data" body, but ideally this should be fixed in the core code

### Actual Behavior

Only client_id is passed

### Steps to Reproduce

...

### Debug Logs

```powershell
...
```

### Other

_No response_