The public booking page showed a capped flat preview of slots with no way
to pick a service, day, or staff member. Replaces it with a stepped flow:
pick service, optional staff preference, pick a day, pick a time.
Backend: availability accepts serviceId/staffId/date filters (default
response unchanged for the embed widget), a new public catalog endpoint
exposes bookable services and active staff, and slots carry staffName.
Slot generation and booking creation now honor tenant-wide and per-staff
blocked days; appointment requests must fit inside a matching
availability rule and reference tenant-owned, active staff and locations.
Generated with [Devin](https://devin.ai)
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
