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- remove setup-ssl.sh (mkcert IP certs) - superseded by install.sh's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>

install.sh

@@ -61,7 +61,7 @@ if [ ! -f "$SCRIPT_DIR/.env" ]; then
     echo "        A .env file has been created from .env.example."
     echo "        You must fill in SITE_ID, SITE_KEY, and SECRET_KEY before starting."
     echo ""
-    echo "        Get SITE_ID and SITE_KEY from: https://xenia-admin.bonamin.gr"
+    echo "        Get SITE_ID and SITE_KEY from: https://xenia-admin.bonamin.net"
     echo "        Generate SECRET_KEY with:  openssl rand -hex 32"
     echo ""