- Add SearchRoutes method to yandex client for on-demand station pair searches
- Implement hub expansion via on-demand /search calls in lazy graph expansion
- Integrate cache key generation for search results (search:{from}:{to}:{date})
- Update expandFromStation and expandFromCityHub to use Yandex API
- Add NewGraphWithoutYandex constructor for testability
- Add tests for on-demand search integration and cache TTL policies
- Create cmd/api/handlers.go with HTTP handlers for all MVP endpoints
- Implement GET /v1/cities?query= city autocomplete
- Implement GET /v1/cities/{id}/stations city stations including neighbors
- Implement POST /v1/routes/search route search with Pareto-optimal results
- Implement GET /v1/routes/{search_id}/{route_id}/geojson route geometry
- Implement GET /v1/stations/{id}/status station status endpoint
- Add handler tests with success and error cases
- All existing tests pass
