fix(GRO-636): input validation fixes for 5 API routes

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>

apps/api/src/routes/appointments.ts

@@ -41,6 +41,10 @@ const createAppointmentSchema = z.object({
       frequencyWeeks: z.number().int().min(1).max(52),
       count: z.number().int().min(2).max(52),
     })
+    .refine(
+      (r) => r.frequencyWeeks * r.count <= 52,
+      { message: "Recurrence series must not exceed 1 year" }
+    )
     .optional(),
 });