- Add Cost field to Edge and RouteLeg structs
- Propagate Cost in FindRoute itinerary creation
- Write TestRouteParetoRanking test verifying non-dominated route selection
- Add addSyntheticEdgesForNode function that connects nodes to city hubs
- Modify FindRoute to add synthetic edges as fallback when no route found
- Write TestFindRouteWithSyntheticFallback test
Co-Authored-By: Claude <noreply@anthropic.com>