Admin Services tab: create/edit services (name, desc, price, scheduling type)

**Sprint 2 - Admin Dashboard & Services**

Implement the Admin Services tab functionality:
- Admin can add new services and edit existing ones
- Set service name, description, and price
- Choose whether the service has a preset date or client-led scheduling
- Services auto-created on Stripe when added
- DB/JSON structure for services
- Estimated: 10 hours