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/PropertyCardCompact.tsx

@@ -37,7 +37,7 @@ export function PropertyCardCompact({
                 {property.photo_thumbnail && (
                     <img
                         src={property.photo_thumbnail}
-                        alt="Property"
+                        alt={`${property.rooms}-bed, £${property.total_price.toLocaleString()}`}
                         className="w-full h-full object-cover"
                     />
                 )}