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/DependencyInjection/ConfigurableExtension.php

@@ -0,0 +1,39 @@
+<?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\DependencyInjection;
+
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+/**
+ * This extension sub-class provides first-class integration with the
+ * Config/Definition Component.
+ *
+ * You can use this as base class if
+ *
+ *    a) you use the Config/Definition component for configuration,
+ *    b) your configuration class is named "Configuration", and
+ *    c) the configuration class resides in the DependencyInjection sub-folder.
+ *
+ * @author Johannes M. Schmitt <schmittjoh@gmail.com>
+ */
+abstract class ConfigurableExtension extends Extension
+{
+    final public function load(array $configs, ContainerBuilder $container): void
+    {
+        $this->loadInternal($this->processConfiguration($this->getConfiguration($configs, $container), $configs), $container);
+    }
+
+    /**
+     * Configures the passed container according to the merged configuration.
+     */
+    abstract protected function loadInternal(array $mergedConfig, ContainerBuilder $container): void;
+}