chore: label waiter domain as legacy in sysadmin; document bonamin.net hosts

Per-client domains are retired (client-services plan step 9); the field
and column stay for sites not yet migrated (never drop columns).
Documents xenia-api / xenia-admin / registry .bonamin.net.

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

sysadmin_panel/src/pages/SiteDetailPage.jsx

@@ -328,7 +328,9 @@ export default function SiteDetailPage() {
       {/* Waiter Domain */}
       <div className="bg-gray-900 border border-gray-700 rounded-xl p-4 mb-4">
         <div className="flex items-center justify-between mb-3">
-          <h2 className="text-xs font-semibold text-gray-500 uppercase tracking-wider">Waiter Domain</h2>
+          {/* Retired per-client domain setup (client-services plan step 9) — kept only for sites
+              not yet migrated; new sites use http://<LAN IP> and the pairing QR in the manager */}
+          <h2 className="text-xs font-semibold text-gray-500 uppercase tracking-wider">Waiter Domain (legacy — not needed for new sites)</h2>
           <button
             onClick={() => { setNewDomain(site.waiter_domain || ''); setModal('domain') }}
             className="text-xs text-cyan-400 hover:text-cyan-300 transition-colors"