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.tsx

@@ -603,15 +603,18 @@ export const MapView = memo(function MapView({
         {markers}
       </MarkerClusterGroup>
 
-      {route && route.length > 1 && (
+      {route && route.length > 0 && (
         <>
-          <Polyline
-            positions={route}
-            color="#111827"
-            weight={3}
-            opacity={0.9}
-            dashArray="6, 5"
-          />
+          {route.map((seg, i) => seg.length > 1 && (
+            <Polyline
+              key={i}
+              positions={seg}
+              color="#111827"
+              weight={3}
+              opacity={0.9}
+              dashArray="6, 5"
+            />
+          ))}
           {routeSegments.map((seg, i) => (
             <RouteLabel key={i} midpoint={seg.mid} from={seg.from} to={seg.to} walkingText={seg.walkingText} drivingText={seg.drivingText} />
           ))}