feat: multi-select category filter, performance fixes, check-in/out order

- Category filter is now a multi-select dropdown with checkboxes
- PlaceAvatar: replace 200ms polling intervals with event-based
  notification + React.memo for major performance improvement
- Map photo fetches: concurrency limited to 3 + lazy loading on images
- PlacesSidebar: content-visibility + useMemo for smooth scrolling
- Accommodation labels: check-out now appears before check-in on same day
- Timed places auto-sort chronologically when time is added

client/src/i18n/translations/de.ts

@@ -647,6 +647,8 @@ const de: Record<string, string | { name: string; category: string }[]> = {
   'places.unplanned': 'Ungeplant',
   'places.search': 'Orte suchen...',
   'places.allCategories': 'Alle Kategorien',
+  'places.categoriesSelected': 'Kategorien',
+  'places.clearFilter': 'Filter zurücksetzen',
   'places.count': '{count} Orte',
   'places.countSingular': '1 Ort',
   'places.allPlanned': 'Alle Orte sind eingeplant',

client/src/i18n/translations/en.ts

@@ -647,6 +647,8 @@ const en: Record<string, string | { name: string; category: string }[]> = {
   'places.unplanned': 'Unplanned',
   'places.search': 'Search places...',
   'places.allCategories': 'All Categories',
+  'places.categoriesSelected': 'categories',
+  'places.clearFilter': 'Clear filter',
   'places.count': '{count} places',
   'places.countSingular': '1 place',
   'places.allPlanned': 'All places are planned',