server {
    listen       80;
    server_name  _;
    root         /usr/share/nginx/html;
    index        index.html;

    gzip            on;
    gzip_types      text/css application/javascript image/svg+xml;
    gzip_min_length 256;

    # Static assets: cache for a week (filenames are stable for this app).
    location ~* \.(css|js|svg|png|ico)$ {
        add_header X-Content-Type-Options "nosniff" always;
        add_header X-Frame-Options "SAMEORIGIN" always;
        add_header Referrer-Policy "no-referrer-when-downgrade" always;
        add_header Cache-Control "public, max-age=604800";
    }

    # HTML entry point: always revalidate so redeploys show up immediately.
    location / {
        add_header X-Content-Type-Options "nosniff" always;
        add_header X-Frame-Options "SAMEORIGIN" always;
        add_header Referrer-Policy "no-referrer-when-downgrade" always;
        add_header Cache-Control "no-cache" always;
        try_files $uri $uri/ /index.html;
    }
}