VNC Proxy Worker.
        
Endpoints:
- /vnc/connect?sessionId=xxx      - Original: Dashboard viewer via Cloudflare Tunnel
- /vnc/relay/device?sessionId=xxx - New: Android device connects here
- /vnc/relay/viewer?sessionId=xxx - New: Dashboard viewer connects here
- /vnc/relay/status?sessionId=xxx - New: Check relay status
- /health                          - Worker health check