Covers: notify_parent() on AdminNotifier, multipart HTML email with
inline Swiss QR-bill (qrbill library), CHF 80 fixed payment data,
German default language, best-effort error handling.
https://claude.ai/code/session_01LjjK7RjKVnC8bETtccfgna
Parents currently receive no confirmation after submitting a registration.
This change adds an HTML confirmation email with full registration summary,
payment instructions, and a Swiss QR-bill for the CHF 80 registration fee.
https://claude.ai/code/session_01LjjK7RjKVnC8bETtccfgna
Creates the OpenSpec change directory for sending HTML confirmation
emails to parents on registration completion, including payment
instructions and Swiss QR-bill code.
https://claude.ai/code/session_01LjjK7RjKVnC8bETtccfgna