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/mime/Encoder/QpContentEncoder.php

@@ -0,0 +1,55 @@
+<?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\Mime\Encoder;
+
+/**
+ * @author Lars Strojny
+ */
+final class QpContentEncoder implements ContentEncoderInterface
+{
+    public function encodeByteStream($stream, int $maxLineLength = 0): iterable
+    {
+        if (!\is_resource($stream)) {
+            throw new \TypeError(\sprintf('Method "%s" takes a stream as a first argument.', __METHOD__));
+        }
+
+        // we don't use PHP stream filters here as the content should be small enough
+        yield $this->encodeString(stream_get_contents($stream), 'utf-8', 0, $maxLineLength);
+    }
+
+    public function getName(): string
+    {
+        return 'quoted-printable';
+    }
+
+    public function encodeString(string $string, ?string $charset = 'utf-8', int $firstLineOffset = 0, int $maxLineLength = 0): string
+    {
+        return $this->standardize(quoted_printable_encode($string));
+    }
+
+    /**
+     * Make sure CRLF is correct and HT/SPACE are in valid places.
+     */
+    private function standardize(string $string): string
+    {
+        // transform CR or LF to CRLF
+        $string = preg_replace('~=0D(?!=0A)|(?<!=0D)=0A~', '=0D=0A', $string);
+        // transform =0D=0A to CRLF
+        $string = str_replace(["\t=0D=0A", ' =0D=0A', '=0D=0A'], ["=09\r\n", "=20\r\n", "\r\n"], $string);
+
+        return match ($string[-1] ?? '') {
+            "\x09" => substr_replace($string, '=09', -1),
+            "\x20" => substr_replace($string, '=20', -1),
+            default => $string,
+        };
+    }
+}