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/container/src/ContainerInterface.php

@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psr\Container;
+
+/**
+ * Describes the interface of a container that exposes methods to read its entries.
+ */
+interface ContainerInterface
+{
+    /**
+     * Finds an entry of the container by its identifier and returns it.
+     *
+     * @param string $id Identifier of the entry to look for.
+     *
+     * @throws NotFoundExceptionInterface  No entry was found for **this** identifier.
+     * @throws ContainerExceptionInterface Error while retrieving the entry.
+     *
+     * @return mixed Entry.
+     */
+    public function get(string $id);
+
+    /**
+     * Returns true if the container can return an entry for the given identifier.
+     * Returns false otherwise.
+     *
+     * `has($id)` returning true does not mean that `get($id)` will not throw an exception.
+     * It does however mean that `get($id)` will not throw a `NotFoundExceptionInterface`.
+     *
+     * @param string $id Identifier of the entry to look for.
+     *
+     * @return bool
+     */
+    public function has(string $id): bool;
+}