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

    # SPA fallback — serve index.html for all routes that don't match a file.
    location / {
        try_files $uri $uri/ /index.html;
    }

    # Runtime config generated by the entrypoint — don't cache.
    location = /config.json {
        add_header Cache-Control "no-cache";
    }

    # OAuth client metadata must be fetchable cross-origin by auth servers.
    location = /client-metadata.json {
        add_header Access-Control-Allow-Origin *;
        add_header Cache-Control "public, max-age=300";
    }

    # Security headers (mirrors public/_headers for Cloudflare Pages).
    add_header X-Frame-Options DENY;
    add_header X-Content-Type-Options nosniff;
    add_header Referrer-Policy strict-origin-when-cross-origin;
    add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; font-src 'self' https://fonts.gstatic.com; img-src 'self' data: https:; connect-src 'self' https:; frame-ancestors 'none'; base-uri 'self'; form-action 'self'";
}