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/error-handler/Error/UndefinedFunctionError.php

@@ -0,0 +1,29 @@
+<?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\ErrorHandler\Error;
+
+class UndefinedFunctionError extends \Error
+{
+    public function __construct(string $message, \Throwable $previous)
+    {
+        parent::__construct($message, $previous->getCode(), $previous->getPrevious());
+
+        foreach ([
+            'file' => $previous->getFile(),
+            'line' => $previous->getLine(),
+            'trace' => $previous->getTrace(),
+        ] as $property => $value) {
+            $refl = new \ReflectionProperty(\Error::class, $property);
+            $refl->setValue($this, $value);
+        }
+    }
+}