feat: add multi-day transport reservations with dedicated modal and route segmentation

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

client/src/components/Map/MapView.test.tsx

@@ -124,7 +124,7 @@ describe('MapView', () => {
   })
 
   it('FE-COMP-MAPVIEW-006: renders polyline when route has 2+ points', () => {
-    render(<MapView route={[[48.0, 2.0], [49.0, 3.0]]} />)
+    render(<MapView route={[[[48.0, 2.0], [49.0, 3.0]]]} />)
     expect(screen.getByTestId('polyline')).toBeTruthy()
   })
 
@@ -134,7 +134,7 @@ describe('MapView', () => {
   })
 
   it('FE-COMP-MAPVIEW-008: does not render polyline for single-point route', () => {
-    render(<MapView route={[[48.0, 2.0]]} />)
+    render(<MapView route={[[[48.0, 2.0]]]} />)
     expect(screen.queryByTestId('polyline')).toBeNull()
   })
 
@@ -153,7 +153,7 @@ describe('MapView', () => {
   })
 
   it('FE-COMP-MAPVIEW-011: renders RouteLabel marker when routeSegments provided with route', () => {
-    const route = [[48.0, 2.0], [49.0, 3.0]] as [number, number][]
+    const route = [[[48.0, 2.0], [49.0, 3.0]]] as [number, number][][][]
     const routeSegments = [
       { mid: [48.5, 2.5] as [number, number], from: 0, to: 1, walkingText: '10 min', drivingText: '3 min' },
     ]