Add tap-to-detail on swipe cards and fix color overlay alignment

- Add onTap callback to SwipeCard using useDrag's tap detection
- Wire through SwipeReviewMode to open ListingDetailSheet on tap
- Fix color overlay misalignment: add relative to card container so
  the absolute overlay positions within the rounded card, not the
  full-width outer wrapper

frontend/src/components/SwipeReviewMode.tsx

@@ -9,6 +9,7 @@ interface SwipeReviewModeProps {
   onDecide: (listingId: number, decision: DecisionType, listingType?: 'RENT' | 'BUY') => void;
   onClear: (listingId: number, listingType?: 'RENT' | 'BUY') => void;
   onClose: () => void;
+  onSelectListing?: (listingId: number) => void;
   getDecision: (listingId: number, listingType?: string) => DecisionType | undefined;
 }
 
@@ -33,6 +34,7 @@ export function SwipeReviewMode({
   onDecide,
   onClear,
   onClose,
+  onSelectListing,
   getDecision,
 }: SwipeReviewModeProps) {
   // Filter to only undecided features
@@ -128,6 +130,7 @@ export function SwipeReviewMode({
                 key={feature.properties.url}
                 feature={feature}
                 onSwipe={handleSwipe}
+                onTap={() => onSelectListing?.(getListingId(feature))}
                 isTop={i === 0}
                 stackIndex={i}
               />