nginx.conf

server {
    listen 80;
    root /usr/share/nginx/html;
    server_tokens off;

    gzip on;
    gzip_types text/css application/javascript application/json image/svg+xml;
    gzip_min_length 1024;

    # Security headers for the SPA (the API sets its own).
    add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; connect-src 'self'; font-src 'self'; frame-ancestors 'none'; base-uri 'self'; form-action 'self'" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header Referrer-Policy "same-origin" always;
    add_header Permissions-Policy "camera=(), microphone=(), geolocation=()" always;
    add_header X-Frame-Options "DENY" always;

    location = /healthz {
        access_log off;
        default_type text/plain;
        return 200 "ok";
    }

    location /api/ {
        proxy_pass ${API_URL};
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Request-ID $request_id;
        proxy_read_timeout 60s;
        client_max_body_size 6m;
    }

    # Hashed bundles never change: cache for a year.
    location /assets/ {
        add_header Cache-Control "public, max-age=31536000, immutable";
        add_header X-Content-Type-Options "nosniff" always;
        try_files $uri =404;
    }

    # The HTML shell must revalidate so new deploys are picked up.
    location / {
        add_header Cache-Control "no-cache";
        add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; connect-src 'self'; font-src 'self'; frame-ancestors 'none'; base-uri 'self'; form-action 'self'" always;
        add_header X-Content-Type-Options "nosniff" always;
        add_header Referrer-Policy "same-origin" always;
        add_header X-Frame-Options "DENY" always;
        try_files $uri /index.html;
    }
}