Fix Paystack Fullscreen permission policy for Inline iframes.

Pre-set allow=fullscreen on Paystack iframes before navigation (createElement
hook + MutationObserver on allow/src/id), re-apply if Paystack overwrites
allow, and send Permissions-Policy HTTP headers so checkout.paystack.com can
use fullscreen inside the in-app sheet.

app/Http/Middleware/PaystackPermissionsPolicy.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Closure;
+use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\Response;
+
+/**
+ * Delegate payment-related browser features to Paystack Inline iframes.
+ *
+ * Cross-origin checkout.paystack.com needs the top-level document to allow
+ * fullscreen (and payment/clipboard) via Permissions-Policy. Meta tags are
+ * not reliably honored — this must be an HTTP response header.
+ */
+class PaystackPermissionsPolicy
+{
+    public const HEADER_VALUE = 'payment=*, fullscreen=*, clipboard-read=*, clipboard-write=*, publickey-credentials-get=*';
+
+    public function handle(Request $request, Closure $next): Response
+    {
+        /** @var Response $response */
+        $response = $next($request);
+
+        if (! $response->headers->has('Permissions-Policy')) {
+            $response->headers->set('Permissions-Policy', self::HEADER_VALUE);
+        }
+
+        return $response;
+    }
+}