Fix invoice date to use request.created instead of current date

[TaprootFreak]

Summary

• Fix invoice date for pending transactions showing current date instead of transaction creation date
• Changed date: new Date() to date: request.created in createInvoiceFromRequest()

Problem

Invoice PDF showed "Zug 22.1.2026" (today) instead of "Zug 19.1.2026" (when transaction was created)

Fix

Use request.created instead of new Date() in swiss-qr.service.ts:77