classes-logic.ts: effectiveCapacity (session override > class > unlimited),
computeSignupStatus (registered vs waitlisted), sessionTiming, canSignUp
eligibility, pickPromotion (earliest waitlisted when a seat frees).
Dependency-free, 10 unit tests (suite 372 -> 382).
validations.ts: class/session/signup/attendance schemas. payment_link is
a generic http(s) link only (empty -> null); capacity is a positive int;
no live payment integration.
Moheeb Zara
dc23e9261f