specs/registration-notifications/spec.md:
- MODIFIED: parent confirmation email sent on completion (alongside admin)
- Bilingual body (de/en), QR-bill embedded inline, plain-text fallback
- Language persisted as metadata.language in registration record
tasks.md:
- 6 sections: qrbill dep, language persistence, notify_parent() impl,
wire into both completion sites (email agent + chat), tests, smoke test
https://claude.ai/code/session_01LjjK7RjKVnC8bETtccfgna