server {
    listen 80;
    server_name _;

    root /usr/share/nginx/html;
    index index.html;

    # SPA routing: serve index.html for any non-API, non-asset path.
    location / {
        try_files $uri $uri/ /index.html;
    }

    # REST API proxy (spec section 4: frontend -> backend over frontend-net).
    location /api/ {
        proxy_pass http://mqtt-backend:8000;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Real-IP $remote_addr;
    }
}