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/mime/Header/DateHeader.php

@@ -0,0 +1,62 @@
+<?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\Mime\Header;
+
+/**
+ * A Date MIME Header.
+ *
+ * @author Chris Corbyn
+ */
+final class DateHeader extends AbstractHeader
+{
+    private \DateTimeImmutable $dateTime;
+
+    public function __construct(string $name, \DateTimeInterface $date)
+    {
+        parent::__construct($name);
+
+        $this->setDateTime($date);
+    }
+
+    /**
+     * @param \DateTimeInterface $body
+     */
+    public function setBody(mixed $body): void
+    {
+        $this->setDateTime($body);
+    }
+
+    public function getBody(): \DateTimeImmutable
+    {
+        return $this->getDateTime();
+    }
+
+    public function getDateTime(): \DateTimeImmutable
+    {
+        return $this->dateTime;
+    }
+
+    /**
+     * Set the date-time of the Date in this Header.
+     *
+     * If a DateTime instance is provided, it is converted to DateTimeImmutable.
+     */
+    public function setDateTime(\DateTimeInterface $dateTime): void
+    {
+        $this->dateTime = \DateTimeImmutable::createFromInterface($dateTime);
+    }
+
+    public function getBodyAsString(): string
+    {
+        return $this->dateTime->format(\DateTimeInterface::RFC2822);
+    }
+}