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/node_modules/loupe/lib/string.d.ts.map

@@ -0,0 +1 @@
+{"version":3,"file":"string.d.ts","sourceRoot":"","sources":["../src/string.ts"],"names":[],"mappings":"AACA,OAAO,KAAK,EAAE,OAAO,EAAE,MAAM,YAAY,CAAA;AA2BzC,MAAM,CAAC,OAAO,UAAU,aAAa,CAAC,MAAM,EAAE,MAAM,EAAE,OAAO,EAAE,OAAO,GAAG,MAAM,CAK9E"}