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- remove setup-ssl.sh (mkcert IP certs) - superseded by install.sh's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

.env.example

@@ -1,11 +1,11 @@
 # Registry
-REGISTRY=registry.bonamin.gr
+REGISTRY=registry.bonamin.net
 VERSION=0.1.0
 
 # Backend runtime secrets (get SITE_ID and SITE_KEY from the sysadmin panel)
 SITE_ID=your-site-id
 SITE_KEY=your-site-key
-CLOUD_URL=https://xenia-admin.bonamin.gr
+CLOUD_URL=https://xenia-api.bonamin.net
 SECRET_KEY=generate-with-openssl-rand-hex-32
 LICENSE_GRACE_HOURS=24