Add calendar-based booking system: accounts, availability, admin calendar
- Customer accounts (separate auth collection) with /konto area
- Availability + AvailabilityOverrides collections driving real slot calculation
- BookingRequests with race-safe confirmation (Postgres advisory lock + transaction)
- Booking emails (request received, admin notify, confirmed, rejected, alternative proposed/accepted, cancelled)
- Confirmed online bookings auto-create a private linked video-call Event
- Custom Payload admin calendar view (month grid + day schedule)
- Wired booking widget into offer pages and /termin-buchen
maro
5d83c0dc1e