- Add three error display elements with test IDs: departure-error, same-city-error, validation-error
- Add validation state management: departureError, arrivalError, sameAirportError, searchValidationError
- Add validateDepartureInput() function for input validation (reuses validateCityCode)
- Implement same-city validation in useEffect to detect duplicate departure/arrival
- Update handleSearch() to check all required fields and show validation-error when missing
- Add error styling: .route-filter__error with red text (#d32f2f), light red background (#ffebee), and left border
- Same-city error shows inline below arrival input
- Search validation error displays below action buttons
- Errors automatically clear when conditions are fixed
gnezim
a3e5ee9bdd