Add Brotli compression + enable gzip_static / brotli_static

[sylvesterdamgaard]

Motivation

The current nginx in the base images supports gzip but not Brotli, and neither gzip_static nor brotli_static is wired up.

• Brotli typically delivers 15–20% better compression than gzip at the same CPU budget. Universally supported in modern browsers (Chrome, Firefox, Safari, Edge — including Safari since 11).
• Pre-compressed asset serving (gzip_static on / brotli_static on) lets nginx ship the pre-built .gz / .br file straight from disk. Modern build tools (Vite, Webpack, Rollup, esbuild plugins) already produce them as part of the build. Skipping the compression step on every request is a real CPU saving on busy sites — and a moderate latency win even on quiet ones.

Proposal

• Compile ngx_brotli into the nginx build for all php-fpm-nginx variants
• Default brotli on; brotli_comp_level 6; (matches gzip default level)
• Default gzip_static on; brotli_static on; so pre-compressed assets are auto-served when present
• Surface env vars in line with existing gzip ones:
  • NGINX_BROTLI (default on)
  • NGINX_BROTLI_COMP_LEVEL (default 6)
  • NGINX_BROTLI_TYPES (default mirrors NGINX_GZIP_TYPES)
  • NGINX_GZIP_STATIC / NGINX_BROTLI_STATIC (default on)

Acceptance criteria

• brotli directives available
• gzip_static / brotli_static enabled by default
• Env vars documented
• Config validation passes when neither .gz nor .br files are present (graceful fallback to dynamic compression)