- getAppointmentSlots uses doctor_uuid + date (was doctor_id, which the
backend rejects with دکتر یافت نشد).
- postAppointmentPayment posts to /api/v1/payment/appointment (was the
nonexistent /api/v1/payment).
- Remove getAppointmentNotAvailable: the not-available route does not
exist (404); disabled dates come from the slots response.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>