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>

ai/supervisor-nginx.conf

@@ -0,0 +1,38 @@
+events {
+    worker_connections 1024;
+}
+
+http {
+    # Proxy settings
+    proxy_http_version 1.1;
+    proxy_buffering off;
+    proxy_set_header Host $host;
+    proxy_set_header X-Real-IP $remote_addr;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_set_header X-Forwarded-Proto $scheme;
+
+    # Timeouts for Supervisor web UI (quick responses)
+    proxy_connect_timeout 60;
+    proxy_send_timeout 60;
+    proxy_read_timeout 60;
+    send_timeout 60;
+
+    server {
+        listen 80;
+        server_name _;
+
+        location / {
+            # Proxy to Supervisor on RunPod via Tailscale
+            proxy_pass http://${SUPERVISOR_BACKEND_HOST}:${SUPERVISOR_BACKEND_PORT};
+
+            # Proxy headers
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+            proxy_set_header X-Forwarded-Proto $scheme;
+
+            # Disable buffering for real-time updates
+            proxy_buffering off;
+        }
+    }
+}