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/guzzlehttp/guzzle/src/Exception/BadResponseException.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace GuzzleHttp\Exception;
+
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
+
+/**
+ * Exception when an HTTP error occurs (4xx or 5xx error)
+ */
+class BadResponseException extends RequestException
+{
+    public function __construct(
+        string $message,
+        RequestInterface $request,
+        ResponseInterface $response,
+        ?\Throwable $previous = null,
+        array $handlerContext = []
+    ) {
+        parent::__construct($message, $request, $response, $previous, $handlerContext);
+    }
+
+    /**
+     * Current exception and the ones that extend it will always have a response.
+     */
+    public function hasResponse(): bool
+    {
+        return true;
+    }
+
+    /**
+     * This function narrows the return type from the parent class and does not allow it to be nullable.
+     */
+    public function getResponse(): ResponseInterface
+    {
+        /** @var ResponseInterface */
+        return parent::getResponse();
+    }
+}