chore: retire the per-client domain setup (plan step 9); addresses → bonamin.net

- remove setup-ssl.sh (mkcert IP certs) - superseded by install.sh's
  self-signed cert and the backend-managed TLS identity
- manager: "Waiter Domain (παλιό σύστημα)" - shown only for sites that
  still have one
- .env.example: REGISTRY=registry.bonamin.net and
  CLOUD_URL=https://xenia-api.bonamin.net (it pointed at the admin panel,
  xenia-admin, even before the domain move); install.sh points to the
  sysadmin panel at xenia-admin.bonamin.net
- pack README registry example updated
Proxy config unchanged (HTTPS domain blocks stay so not-yet-migrated sites
keep working until their visit).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

manager_dashboard/src/pages/Settings/tabs/AppInfoTab.jsx

@@ -557,7 +557,8 @@ export default function AppInfoTab() {
           )}
           {status?.waiter_domain && (
             <>
-              <div className="text-gray-500">Waiter Domain</div>
+              {/* Retired per-client domain setup (plan step 9): shown only for sites that still have one */}
+              <div className="text-gray-500">Waiter Domain (παλιό σύστημα)</div>
               <div className="flex items-center gap-2 flex-wrap">
                 <span className="font-medium text-gray-800 text-xs font-mono break-all">{status.waiter_domain}</span>
                 <button