v2.1.0 — Real-time collaboration, performance & security overhaul

Real-Time Collaboration (WebSocket):
- WebSocket server with JWT auth and trip-based rooms
- Live sync for all CRUD operations (places, assignments, days, notes, budget, packing, reservations, files)
- Socket-based exclusion to prevent duplicate updates
- Auto-reconnect with exponential backoff
- Assignment move sync between days

Performance:
- 16 database indexes on all foreign key columns
- N+1 query fix in places, assignments and days endpoints
- Marker clustering (react-leaflet-cluster) with configurable radius
- List virtualization (react-window) for places sidebar
- useMemo for filtered places
- SQLite WAL mode + busy_timeout for concurrent writes
- Weather API: server-side cache (1h forecast, 15min current) + client sessionStorage
- Google Places photos: persisted to DB after first fetch
- Google Details: 3-tier cache (memory → sessionStorage → API)

Security:
- CORS auto-configuration (production: same-origin, dev: open)
- API keys removed from /auth/me response
- Admin-only endpoint for reading API keys
- Path traversal prevention in cover image deletion
- JWT secret persisted to file (survives restarts)
- Avatar upload file extension whitelist
- API key fallback: normal users use admin's key without exposure
- Case-insensitive email login

Dark Mode:
- Fixed hardcoded colors across PackingList, Budget, ReservationModal, ReservationsPanel
- Mobile map buttons and sidebar sheets respect dark mode
- Cluster markers always dark

UI/UX:
- Redesigned login page with animated planes, stars and feature cards
- Admin: create user functionality with CustomSelect
- Mobile: day-picker popup for assigning places to days
- Mobile: touch-friendly reorder buttons (32px targets)
- Mobile: responsive text (shorter labels on small screens)
- Packing list: index-based category colors
- i18n: translated date picker placeholder, fixed German labels
- Default map tile: CartoDB Light

client/src/components/Planner/PlaceInspector.jsx

@@ -8,14 +8,31 @@ import { useTranslation } from '../../i18n'
 
 const detailsCache = new Map()
 
+function getSessionCache(key) {
+  try {
+    const raw = sessionStorage.getItem(key)
+    return raw ? JSON.parse(raw) : undefined
+  } catch { return undefined }
+}
+
+function setSessionCache(key, value) {
+  try { sessionStorage.setItem(key, JSON.stringify(value)) } catch {}
+}
+
 function useGoogleDetails(googlePlaceId, language) {
   const [details, setDetails] = useState(null)
-  const cacheKey = `${googlePlaceId}_${language}`
+  const cacheKey = `gdetails_${googlePlaceId}_${language}`
   useEffect(() => {
     if (!googlePlaceId) { setDetails(null); return }
+    // In-memory cache (fastest)
     if (detailsCache.has(cacheKey)) { setDetails(detailsCache.get(cacheKey)); return }
+    // sessionStorage cache (survives reload)
+    const cached = getSessionCache(cacheKey)
+    if (cached) { detailsCache.set(cacheKey, cached); setDetails(cached); return }
+    // Fetch from API
     mapsApi.details(googlePlaceId, language).then(data => {
       detailsCache.set(cacheKey, data.place)
+      setSessionCache(cacheKey, data.place)
       setDetails(data.place)
     }).catch(() => {})
   }, [googlePlaceId, language])