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/translation/Loader/LoaderInterface.php

@@ -0,0 +1,32 @@
+<?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\Translation\Loader;
+
+use Symfony\Component\Translation\Exception\InvalidResourceException;
+use Symfony\Component\Translation\Exception\NotFoundResourceException;
+use Symfony\Component\Translation\MessageCatalogue;
+
+/**
+ * LoaderInterface is the interface implemented by all translation loaders.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+interface LoaderInterface
+{
+    /**
+     * Loads a locale.
+     *
+     * @throws NotFoundResourceException when the resource cannot be found
+     * @throws InvalidResourceException  when the resource cannot be loaded
+     */
+    public function load(mixed $resource, string $locale, string $domain = 'messages'): MessageCatalogue;
+}