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/store/authStore.js

@@ -1,5 +1,6 @@
 import { create } from 'zustand'
 import { authApi } from '../api/client'
+import { connect, disconnect } from '../api/websocket'
 
 export const useAuthStore = create((set, get) => ({
   user: null,
@@ -20,6 +21,7 @@ export const useAuthStore = create((set, get) => ({
         isLoading: false,
         error: null,
       })
+      connect(data.token)
       return data
     } catch (err) {
       const error = err.response?.data?.error || 'Anmeldung fehlgeschlagen'
@@ -40,6 +42,7 @@ export const useAuthStore = create((set, get) => ({
         isLoading: false,
         error: null,
       })
+      connect(data.token)
       return data
     } catch (err) {
       const error = err.response?.data?.error || 'Registrierung fehlgeschlagen'
@@ -49,6 +52,7 @@ export const useAuthStore = create((set, get) => ({
   },
 
   logout: () => {
+    disconnect()
     localStorage.removeItem('auth_token')
     set({
       user: null,
@@ -72,6 +76,7 @@ export const useAuthStore = create((set, get) => ({
         isAuthenticated: true,
         isLoading: false,
       })
+      connect(token)
     } catch (err) {
       localStorage.removeItem('auth_token')
       set({