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/var-dumper/Caster/ConstStub.php

@@ -0,0 +1,52 @@
+<?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\VarDumper\Caster;
+
+use Symfony\Component\VarDumper\Cloner\Stub;
+
+/**
+ * Represents a PHP constant and its value.
+ *
+ * @author Nicolas Grekas <p@tchwork.com>
+ */
+class ConstStub extends Stub
+{
+    public function __construct(string $name, string|int|float|null $value = null)
+    {
+        $this->class = $name;
+        $this->value = 1 < \func_num_args() ? $value : $name;
+    }
+
+    public function __toString(): string
+    {
+        return (string) $this->value;
+    }
+
+    /**
+     * @param array<int, string> $values
+     */
+    public static function fromBitfield(int $value, array $values): self
+    {
+        $names = [];
+        foreach ($values as $v => $name) {
+            if ($value & $v) {
+                $names[] = $name;
+            }
+        }
+
+        if (!$names) {
+            $names[] = $values[0] ?? 0;
+        }
+
+        return new self(implode(' | ', $names), $value);
+    }
+}