feat: per-subscriber Mailwizz sync button on admin list

Add POST route and form request to queue SyncSubscriberToMailwizz for one
subscriber when the page has Mailwizz configured. Include Dutch strings
and feature tests for auth and edge cases.

Made-with: Cursor

app/Http/Requests/Admin/SyncSubscriberMailwizzRequest.php

@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Requests\Admin;
+
+use App\Models\PreregistrationPage;
+use App\Models\Subscriber;
+use Illuminate\Contracts\Validation\ValidationRule;
+use Illuminate\Foundation\Http\FormRequest;
+
+class SyncSubscriberMailwizzRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        $page = $this->route('page');
+        $subscriber = $this->route('subscriber');
+        if (! $page instanceof PreregistrationPage || ! $subscriber instanceof Subscriber) {
+            return false;
+        }
+
+        if ($subscriber->preregistration_page_id !== $page->id) {
+            return false;
+        }
+
+        return $this->user()?->can('update', $page) ?? false;
+    }
+
+    /**
+     * @return array<string, array<int, ValidationRule|string>>
+     */
+    public function rules(): array
+    {
+        return [];
+    }
+}