Widerruf: Gesetzliche Online-Widerrufsfunktion (Formular, Bestätigungsmail, Admin-Verwaltung)

- Öffentliches Widerrufsformular /widerruf mit Bestell-Lookup (throttled)
- Bestätigungsmail an Kunde + Weiterleitung an bestellungen@ (config app.withdrawal_mail)
- Admin-Übersicht/-Detail unter /admin/withdrawals inkl. Sidenav-Eintrag
- Widerruf-Button in Portal-Bestellansicht und Footer-Links
- Model OrderWithdrawal + Migration + Factory + Tests

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/Http/Requests/Withdrawal/WithdrawalLookupRequest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace App\Http\Requests\Withdrawal;
+
+use Illuminate\Foundation\Http\FormRequest;
+
+class WithdrawalLookupRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    /**
+     * @return array<string, array<int, mixed>>
+     */
+    public function rules(): array
+    {
+        return [
+            'order_number' => ['required', 'string', 'max:50'],
+            'email' => ['required', 'email', 'max:255'],
+        ];
+    }
+
+    /**
+     * @return array<string, string>
+     */
+    public function messages(): array
+    {
+        return [
+            'order_number.required' => __('validation.required', ['attribute' => __('withdrawal.order_number')]),
+            'email.required' => __('validation.required', ['attribute' => __('withdrawal.email')]),
+            'email.email' => __('validation.email', ['attribute' => __('withdrawal.email')]),
+        ];
+    }
+}