Configure Vite proxy and Nginx for WebSocket traffic

[omattsson]

Summary

Update development proxy and production Nginx config to support WebSocket connections on the /ws path.

Tasks

• Modify frontend/vite.config.ts:
  • Add proxy entry for /ws with target: 'http://backend:8081', ws: true, and appropriate headers
• Modify frontend/nginx.conf:
  • Add location /ws block with:
    • proxy_pass http://backend:8081;
    • proxy_http_version 1.1;
    • proxy_set_header Upgrade $http_upgrade;
    • proxy_set_header Connection 'upgrade';
    • proxy_read_timeout 86400s; (prevent Nginx from closing idle WS connections)
• Verify docker-compose.yml needs no port changes (WS runs on same port 8081)

Acceptance Criteria

• WebSocket connects successfully through Vite dev proxy
• WebSocket connects successfully through Nginx in Docker
• No impact on existing REST API proxying