Extract Ladill QR Plus as standalone app at qr.ladill.com.

Utility QR types only (URL, WiFi, link list, business, app download) with
SSO, Billing API integration, public /q resolver, and qr-plus:import for
platform migration. vCard and commerce types stay on the platform.

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

config/identity.php

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