The config:show and config:export tests now include DOKKU_PROXY_PORT
in expected output since ports-configure runs at app creation time.
Add sleep before HTTP assertion in nginx-vhosts_13 test to allow
nginx async reload to complete.
When an app has no web listeners (not yet deployed, no web process type,
or web processes not running), generate a minimal nginx config that
returns 502 Bad Gateway instead of having no config at all. This ensures
domains resolve, monitoring tools detect non-200 status codes, and SSL
certificate provisioning tools like letsencrypt can function.