- Add get_available_slots() and _expand_availability_to_slots() to ExchangeService
- Update routes/exchange.py to use ExchangeService.get_available_slots()
- Remove all business logic from get_available_slots endpoint
- Add AvailabilityRepository to ExchangeService dependencies
- Add Availability and BookableSlot imports to ExchangeService
- Fix import path for validate_date_in_range (use date_validation module)
- Remove unused user_repo variable and import from routes/invites.py
- Fix mypy error in ValidationError by adding proper type annotation
- Create AvailabilityService with get_availability_for_range(), set_availability_for_date(), and copy_availability()
- Move slot validation logic to service
- Update routes/availability.py to use AvailabilityService
- Remove all direct database queries from routes
- Create PriceService with get_recent_prices() and fetch_and_store_price()
- Update routes/audit.py to use PriceService instead of direct queries
- Use PriceHistoryMapper consistently
- Update test to patch services.price.fetch_btc_eur_price
