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/psr/http-client/src/RequestExceptionInterface.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Psr\Http\Client;
+
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Exception for when a request failed.
+ *
+ * Examples:
+ *      - Request is invalid (e.g. method is missing)
+ *      - Runtime request errors (e.g. the body stream is not seekable)
+ */
+interface RequestExceptionInterface extends ClientExceptionInterface
+{
+    /**
+     * Returns the request.
+     *
+     * The request object MAY be a different object from the one passed to ClientInterface::sendRequest()
+     *
+     * @return RequestInterface
+     */
+    public function getRequest(): RequestInterface;
+}