refactor: nginx.conf is source of truth, drop generate script and template

nginx/nginx.conf is symlinked directly into system nginx config.
No need for a per-domain generate script or template — edit the file,
run nginx -t && systemctl reload nginx.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

nginx/nginx.conf

@@ -1,7 +1,3 @@
-# Generated from nginx.conf.template — do not edit directly.
-# Regenerate per domain: sudo ./scripts/generate-nginx-conf.sh <domain>
-# This file is kept as a reference only; production uses sites-available/*.conf
-
 upstream web {
     server 127.0.0.1:8080;
 }