feat: add Supervisor proxy with Authelia SSO

Add nginx reverse proxy service for Supervisor web UI at supervisor.ai.pivoine.art with Authelia authentication. Proxies to RunPod GPU instance via Tailscale (100.121.199.88:9001).

Changes:
- Create supervisor-nginx.conf for nginx proxy configuration
- Add supervisor service to docker-compose with Traefik labels
- Add supervisor.ai.pivoine.art to Authelia protected domains
- Remove deprecated Flux-related files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

net/authelia/configuration.yml

@@ -75,6 +75,7 @@ access_control:
         - "facefusion.ai.pivoine.art"
         - "pinchflat.media.pivoine.art"
         - "comfy.ai.pivoine.art"
+        - "supervisor.ai.pivoine.art"
       policy: one_factor