Add progressive web app companion for cross-platform access

Vite + TypeScript PWA that mirrors the Android app's core features:
- Pre-processed shelter data (build-time UTM33N→WGS84 conversion)
- Leaflet map with shelter markers, user location, and offline tiles
- Canvas compass arrow (ported from DirectionArrowView.kt)
- IndexedDB shelter cache with 7-day staleness check
- Service worker with CacheFirst tiles and precached app shell
- i18n for en, nb, nn (ported from Android strings.xml)
- iOS/Android compass handling with low-pass filter
- Respects user map interaction (no auto-snap on pan/zoom)
- Build revision cache-breaker for reliable SW updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pwa/src/i18n/nb.ts

@@ -0,0 +1,44 @@
+/** Norwegian Bokm\u00e5l strings. Ported from res/values-nb/strings.xml. */
+export const nb: Record<string, string> = {
+  app_name: 'Tilfluktsrom',
+
+  status_ready: 'Klar',
+  status_loading: 'Laster tilfluktsromdata\u2026',
+  status_updating: 'Oppdaterer\u2026',
+  status_offline: 'Frakoblet modus',
+  status_shelters_loaded: '%d tilfluktsrom lastet',
+  status_no_location: 'Venter p\u00e5 GPS\u2026',
+  status_caching_map: 'Lagrer kart for frakoblet bruk\u2026',
+
+  loading_shelters: 'Laster ned tilfluktsromdata\u2026',
+  loading_map: 'Lagrer kartfliser\u2026',
+  loading_map_explanation:
+    'Forbereder frakoblet kart.\nKartet vil rulle kort for \u00e5 lagre omgivelsene dine.',
+  loading_first_time: 'Gj\u00f8r klar for f\u00f8rste gangs bruk\u2026',
+
+  shelter_capacity: '%d plasser',
+  shelter_room_nr: 'Rom %d',
+  nearest_shelter: 'N\u00e6rmeste tilfluktsrom',
+  no_shelters: 'Ingen tilfluktsromdata tilgjengelig',
+
+  action_refresh: 'Oppdater data',
+  action_toggle_view: 'Bytt mellom kart og kompassvisning',
+  action_skip: 'Hopp over',
+  action_cache_ok: 'Lagre kart',
+  action_cache_now: 'Lagre n\u00e5',
+  warning_no_map_cache:
+    'Ingen frakoblet kart lagret. Kartet krever internett.',
+
+  permission_location_title: 'Posisjonstillatelse kreves',
+  permission_location_message:
+    'Denne appen trenger din posisjon for \u00e5 finne n\u00e6rmeste tilfluktsrom. Vennligst gi tilgang til posisjon.',
+  permission_denied:
+    'Posisjonstillatelse avsl\u00e5tt. Appen kan ikke finne tilfluktsrom i n\u00e6rheten uten den.',
+
+  error_download_failed:
+    'Kunne ikke laste ned tilfluktsromdata. Sjekk internettforbindelsen.',
+  error_no_data_offline:
+    'Ingen lagrede data tilgjengelig. Koble til internett for \u00e5 laste ned tilfluktsromdata.',
+  update_success: 'Tilfluktsromdata oppdatert',
+  update_failed: 'Oppdatering mislyktes \u2014 bruker lagrede data',
+};