Stand: SMTP-Test, Admin-Mail-Tab, Notifiable-Fix, Lazy-Quill

- Fix: Notifiable-Trait zum User-Model hinzugefuegt (behebt notify()-500er)
- Installer: SMTP-Verbindungstest mit EsmtpTransport + Ueberspringen-Link
- Admin: Neuer E-Mail-Tab mit SMTP-Konfiguration + Verbindungstest
- Admin: Lazy Quill-Initialisierung (nur sichtbare Locale wird geladen)
- Uebersetzungen: 17 neue Mail-Keys in allen 6 Sprachen

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

vendor/symfony/http-kernel/Exception/UnauthorizedHttpException.php

@@ -0,0 +1,28 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\HttpKernel\Exception;
+
+/**
+ * @author Ben Ramsey <ben@benramsey.com>
+ */
+class UnauthorizedHttpException extends HttpException
+{
+    /**
+     * @param string $challenge WWW-Authenticate challenge string
+     */
+    public function __construct(string $challenge, string $message = '', ?\Throwable $previous = null, int $code = 0, array $headers = [])
+    {
+        $headers['WWW-Authenticate'] = $challenge;
+
+        parent::__construct(401, $message, $previous, $headers, $code);
+    }
+}