Wire Ladill domain picker and purchase modal into hosting flows.

Use the Domains API for owned domains across panel, account, and order forms, with an embedded iframe purchase modal instead of redirecting to domains.ladill.com.

Co-authored-by: Cursor <cursoragent@cursor.com>

config/domains.php

@@ -0,0 +1,6 @@
+<?php
+
+return [
+    'api_url' => env('DOMAINS_API_URL', 'https://domains.ladill.com/api'),
+    'api_key' => env('DOMAINS_API_KEY_HOSTING'),
+];