build(deps): bump websockets from 15.0.1 to 16.1.1 in /backend

Bumps [websockets](https://github.com/python-websockets/websockets) from 15.0.1 to 16.1.1.
- [Release notes](https://github.com/python-websockets/websockets/releases)
- [Commits](https://github.com/python-websockets/websockets/compare/15.0.1...16.1.1)

---
updated-dependencies:
- dependency-name: websockets
  dependency-version: 16.1.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

backend/requirements.txt

@@ -26,7 +26,7 @@ python-socketio==5.16.3
 python-engineio==4.13.3
 # WebSocket CLIENT for the ServerKit Cloud relay (see
 # app/services/connect_client.py). The server-side stack above cannot dial out.
-websockets==15.0.1
+websockets==16.1.1
 
 # System monitoring
 psutil==5.9.7