fix(worker): handle invoice.issued event in discord.notify

The invoices module started enqueueing invoice.issued notifications but
the worker's discord.notify handler had no case for it, causing the job
to exhaust retries and land in needs_review (surfaced on the dashboard
as "Aufträge mit Fehlern / Prüfbedarf").

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/worker/src/jobs.ts

@@ -13,7 +13,8 @@ const handlers: Record<string, Handler> = {
       : p.event === 'backup.stale' ? `⚠ Kein aktuelles Backup: ${p.detail ?? ''}`.trim()
             : p.event === 'restoretest.failed' ? `⚠ Wiederherstellungstest fehlgeschlagen: ${p.detail ?? ''}`.trim()
       : p.event === 'ticket.created' ? `🎫 Neues Ticket ${p.number}: ${p.subject ?? ''}`.trim()
-      : p.event === 'ticket.message' ? `🎫 Neue Nachricht zu Ticket ${p.number}` : null; // keine personenbezogenen Daten
+      : p.event === 'ticket.message' ? `🎫 Neue Nachricht zu Ticket ${p.number}`
+      : p.event === 'invoice.issued' ? `🧾 Rechnung ${p.number} ausgestellt (${(Number(p.gross ?? 0) / 100).toLocaleString('de-DE', { style: 'currency', currency: 'EUR' })})` : null; // keine personenbezogenen Daten
     if (!text) throw new Error(`Unbekanntes Ereignis: ${p.event}`);
     const r = await notifyAdmin(text);
     if (r === 'skipped') return 'übersprungen: Discord nicht konfiguriert';