Raise default response-cache TTL to 48h

Bump proxy_cache_valid from 10m to 48h and match proxy_cache_path
`inactive` (must be >= the TTL or entries evict before expiring).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ops/nginx_conf/proxy.conf

@@ -61,8 +61,8 @@ server {
 	proxy_pass_request_headers on;
 
 	# Response cache. Opt-in per host: $skip_cache is 0 only when the Host
-	# record sets respcache_enabled. Global default TTL lives in nginx.conf;
-	# upstream Cache-Control (private/no-store) is still honored.
+	# record sets respcache_enabled. Global default TTL (48h) lives in
+	# nginx.conf; upstream Cache-Control (private/no-store) is still honored.
 	proxy_cache proxycache;
 	proxy_cache_key $scheme$host$request_uri;
 	proxy_cache_bypass $skip_cache;