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

    # Security headers
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header X-XSS-Protection "1; mode=block" always;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
    add_header Content-Security-Policy "default-src 'self'; script-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self'; connect-src 'self' https:;" always;

    # Gzip
    gzip on;
    gzip_vary on;
    gzip_types text/plain text/css application/json application/javascript text/xml application/xml text/javascript;

    # Static assets — long cache
    location ~* \.(js|css|png|jpg|jpeg|svg|ico|woff2?)$ {
        expires 1y;
        add_header Cache-Control "public, immutable";
    }

    # SPA fallback — all routes served by index.html
    location / {
        try_files $uri $uri/ /index.html;
    }
}