Introduces a TransportModal for creating/editing flight, train, car, and cruise
reservations that span multiple days. Transport entries now break the map route
into disconnected segments so the polyline reflects actual travel legs.
- Add TransportModal with airport/location pickers, multi-day date range, and all transport types
- Extend DB schema with end_day_id on reservations (migration 110) and backfill from existing dates
- Refactor useRouteCalculation to emit [][][number,number] segments split at transport boundaries
- Update MapView, DayPlanSidebar, ReservationsPanel, TripPlannerPage to wire up transport flow
- Add transport i18n keys across all 15 languages
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