The panel frontend is now served straight from nginx/sites-available/*
(static SPA at location /, plus /api + /socket.io proxy). A broken
directive there 502s the whole panel on a real box, and nothing parsed
these configs in CI.
Add scripts/test/test_nginx_conf.sh: stages each vhost (secure +
insecure) against a real nginx, recreating the absolute paths they
reference (a stand-in frontend/dist bundle, the serverkit-locations /
conf.d include dirs, certbot webroot) and a throwaway self-signed cert
for the TLS vhost, then runs `nginx -t`. Skips cleanly (exit 0) where
nginx/openssl/root aren't available, so it's safe on a dev laptop.
Wire it into the Scripts CI `shell` job after the unit suites (installs
nginx + openssl so the step actually runs). shellcheck-clean at warning
severity; bash -n clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>