Improve frontend UI/UX: accessibility, discoverability, and cleanup

- Add prefers-reduced-motion support (global CSS + SwipeCard spring config)
- Add dismissible map click hint overlay with localStorage persistence
- Replace generic image alt text with descriptive property info across 4 components
- Rename filter buttons to clarify intent (Show Matching Listings / Scrape New from Rightmove)
- Fix mobile FAB overlap with bottom sheet via dynamic snap-aware positioning
- Add swipe review onboarding overlay with gesture explanations and button labels
- Delete unused components: AppSidebar, ActiveQuery, SavedView

frontend/src/components/MobileBottomSheet.tsx

@@ -1,4 +1,4 @@
-import { useState, useMemo, useCallback } from 'react';
+import { useState, useMemo, useCallback, useEffect } from 'react';
 import { Drawer } from 'vaul';
 import { MapPin, PoundSterling } from 'lucide-react';
 import { SwipeableCardRow } from './SwipeableCardRow';
@@ -11,6 +11,7 @@ interface MobileBottomSheetProps {
     highlightedPropertyUrl?: string | null;
     onActiveListingChange?: (feature: PropertyFeature | null) => void;
     poiMetricSelection?: { poiId: number; travelMode: string } | null;
+    onSnapChange?: (snap: string | number | null) => void;
 }
 
 function formatCurrency(value: number): string {
@@ -24,10 +25,16 @@ export function MobileBottomSheet({
     highlightedPropertyUrl,
     onActiveListingChange,
     poiMetricSelection,
+    onSnapChange,
 }: MobileBottomSheetProps) {
     const [snap, setSnap] = useState<string | number | null>("148px");
     const [activeCardIndex, setActiveCardIndex] = useState(0);
 
+    // Notify parent when snap changes
+    useEffect(() => {
+        onSnapChange?.(snap);
+    }, [snap, onSnapChange]);
+
     const features = listingData?.features ?? [];
 
     const stats = useMemo(() => {