feat: make ComfyUI backend IP/port configurable via environment variables

- Replace hardcoded IP in comfyui-nginx.conf with env vars
- Add COMFYUI_BACKEND_HOST and COMFYUI_BACKEND_PORT to compose.yaml
- Use envsubst to substitute variables at container startup
- Defaults: 100.121.199.88:8188 (current RunPod Tailscale IP)

ai/comfyui-nginx.conf

@@ -30,7 +30,7 @@ http {
 
         location / {
             # Proxy to ComfyUI on RunPod via Tailscale
-            proxy_pass http://100.121.199.88:8188;
+            proxy_pass http://${COMFYUI_BACKEND_HOST}:${COMFYUI_BACKEND_PORT};
 
             # WebSocket upgrade
             proxy_http_version 1.1;

ai/compose.yaml

@@ -206,8 +206,11 @@ services:
     restart: unless-stopped
     environment:
       TZ: ${TIMEZONE:-Europe/Berlin}
+      COMFYUI_BACKEND_HOST: ${COMFYUI_BACKEND_HOST:-100.121.199.88}
+      COMFYUI_BACKEND_PORT: ${COMFYUI_BACKEND_PORT:-8188}
     volumes:
-      - ./comfyui-nginx.conf:/etc/nginx/nginx.conf:ro
+      - ./comfyui-nginx.conf:/etc/nginx/nginx.conf.template:ro
+    command: /bin/sh -c "envsubst '$${COMFYUI_BACKEND_HOST},$${COMFYUI_BACKEND_PORT}' < /etc/nginx/nginx.conf.template > /etc/nginx/nginx.conf && exec nginx -g 'daemon off;'"
     networks:
       - compose_network
     labels: