Redirect NGINX_ENVSUBST_OUTPUT_DIR to /tmp and update nginx.conf include
path so envsubst works with read_only: true in docker-compose.
Add tmpfs mount for /etc/nginx/conf.d for additional write layer.
Fixes#96
- nginx.conf converted to template processed by envsubst at container start
- BACKEND_URL env var (default: backend:3000) replaces hardcoded container name
- Docker DNS resolver used for dynamic upstream resolution
- Dockerfile copies nginx.conf as template to /etc/nginx/templates/
This prevents frontend breakage when users customize container names
in their docker-compose.yml.
Daniel Volz