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>

app/Http/Middleware/SetLocaleMiddleware.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Carbon\Carbon;
+use Closure;
+use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\Response;
+
+class SetLocaleMiddleware
+{
+    private const SUPPORTED_LOCALES = ['de', 'en', 'pl', 'ru', 'ar', 'tr'];
+
+    public function handle(Request $request, Closure $next): Response
+    {
+        $locale = $this->resolveLocale($request);
+
+        app()->setLocale($locale);
+        Carbon::setLocale($locale);
+
+        return $next($request);
+    }
+
+    private function resolveLocale(Request $request): string
+    {
+        // 1. Eingeloggter User → DB-Präferenz
+        if ($request->user() && in_array($request->user()->locale, self::SUPPORTED_LOCALES)) {
+            return $request->user()->locale;
+        }
+
+        // 2. Session (für Gastseiten)
+        if (session()->has('locale') && in_array(session('locale'), self::SUPPORTED_LOCALES)) {
+            return session('locale');
+        }
+
+        // 3. Fallback
+        return 'de';
+    }
+
+    public static function supportedLocales(): array
+    {
+        return self::SUPPORTED_LOCALES;
+    }
+}