debug: log X-Forwarded-For header explicitly to diagnose NPM passthrough

Authored by: Jack Levy

nginx/nginx.conf

@@ -19,7 +19,7 @@ http {
     # Log format includes real IP, referrer, and user agent
     log_format main '$remote_addr - [$time_local] "$request" '
                     '$status $body_bytes_sent "$http_referer" '
-                    '"$http_user_agent"';
+                    '"$http_user_agent" fwd="$http_x_forwarded_for"';
     access_log /var/log/nginx/access.log main;
 
     # Use Docker's internal DNS; valid=10s forces re-resolution after container restarts.