Add tappable cards, detail bottom sheet, swipe gestures, and favorites view

- Decision types, services (decisionService, listingDetailService), and index exports
- useDecisions hook with optimistic updates and Map-based state
- useListingDetail hook with session-level caching
- PhotoCarousel component using embla-carousel-react
- ListingDetail component with full property info, like/dislike buttons
- ListingDetailSheet using vaul Drawer (slide-up bottom sheet)
- SwipeablePropertyCard with @use-gesture/react and @react-spring/web
- SwipeReviewMode for mobile full-screen swipe review
- FavoritesView with virtualized liked listings and remove button
- App.tsx integration: decision state, client-side disliked filtering, detail sheet, swipe handlers
- ListView conditionally renders SwipeablePropertyCard when handlers provided
- StatsBar adds 'saved' view mode with heart icon
- Header adds liked count indicator
- New deps: vaul, embla-carousel-react, @use-gesture/react, @react-spring/web

frontend/package.json

@@ -44,6 +44,7 @@
     "crossfilter2": "^1.5.4",
     "d3": "^7.9.0",
     "date-fns": "^4.1.0",
+    "embla-carousel-react": "^8.6.0",
     "lucide-react": "^0.515.0",
     "mapbox-gl": "^3.12.0",
     "oidc-client-ts": "^3.2.1",