Monitoring (R5.3): Betriebs-Alerts fuer Scheduler-/Queue-Ausfaelle

OperationalAlert loggt critical + Best-Effort-Mail an MONITORING_ALERT_EMAIL
(Fallback LEGAL_CONTACT_EMAIL, feature-flagged). Alle 6 Scheduler-Tasks mit
onFailure, Queue::failing-Listener; .env.example: LOG_STACK=daily als Prod-Soll.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/Mail/OperationalAlertMail.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace App\Mail;
+
+use Illuminate\Bus\Queueable;
+use Illuminate\Mail\Mailable;
+use Illuminate\Mail\Mailables\Content;
+use Illuminate\Mail\Mailables\Envelope;
+use Illuminate\Queue\SerializesModels;
+
+/**
+ * Betriebs-Alert an das Ops-Postfach (R5.3). Bewusst schlicht und ungebrandet:
+ * es geht um schnelle, verlässliche Zustellung, nicht um CI.
+ */
+class OperationalAlertMail extends Mailable
+{
+    use Queueable, SerializesModels;
+
+    /**
+     * @param  array<string, mixed>  $context
+     */
+    public function __construct(
+        public readonly string $summary,
+        public readonly array $context = [],
+    ) {}
+
+    public function envelope(): Envelope
+    {
+        return new Envelope(
+            subject: '[Monitoring] '.$this->summary,
+        );
+    }
+
+    public function content(): Content
+    {
+        return new Content(
+            text: 'emails.monitoring.alert',
+            with: [
+                'summary' => $this->summary,
+                'context' => $this->context,
+                'appName' => config('app.name'),
+                'environment' => config('app.env'),
+            ],
+        );
+    }
+}