Fix Cache-Control Headers on Nginx

Nginx often ships static files with short or missing Cache-Control, causing repeat downloads or the opposite problem—immutable JS cached forever without hashed filenames. Set long TTLs only for fingerprinted assets; keep HTML at no-cache or short revalidate where auth might vary.

Reverse proxies must forward or strip Set-Cookie carefully: caching private responses is a security issue EdgeFix flags. Align Vary with compression and content negotiation.