Add Ladill Link URL shortener on ladl.link.

Management UI at link.ladill.com with GHS 0.05 per link wallet billing,
click analytics, and legacy fallback to ladill.com/q for QR ecosystem codes.

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

config/billing.php

@@ -2,8 +2,8 @@
 
 return [
     'api_url' => env('BILLING_API_URL', 'https://ladill.com/api/billing'),
-    'api_key' => env('BILLING_API_KEY_QR'),
-    'service' => 'qr',
+    'api_key' => env('BILLING_API_KEY_LINK'),
+    'service' => 'link',
     'wallet_balance_route' => 'wallet.balance',
     'currency' => 'GHS',
 ];