Class + group booking (fitness studio)

Build a class booking site for a small studio.

Core features:
1. Weekly schedule grid, capacity per class
2. Members buy passes or subscription, book classes with credits
3. Waitlist auto-promote on cancel
4. Instructor view: today's roster, checkin
5. Owner dashboard: revenue, attendance

Data: classes, sessions, bookings, passes, waitlist.
Must-haves: cancel window (no refund inside 12h), mobile-first booking.