Wire LadillLink through QrCode model and remaining QR surfaces.

Public URLs, encoded payloads, slug preview, payment callbacks, and asset paths now use ladl.link instead of ladill.com/q/*.

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

config/link.php

@@ -0,0 +1,5 @@
+<?php
+
+return [
+    'public_domain' => env('LINK_PUBLIC_DOMAIN', 'ladl.link'),
+];