Adds Zod validation across 5 API routes:
1. invoices GET / — query param validation (uuid, enum, int bounds)
2. book POST / — future-time refinement on startTime
3. appointments — recurrence series capped at 1 year
4. services — durationMinutes capped at 480 (8 hours)
5. stripe-webhooks — UUID validation on invoice IDs before DB lookup
Closes GRO-636
Co-Authored-By: Paperclip <noreply@paperclip.ing>
groombook-cto[bot]
e1e13d5091