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/caniuse-lite/dist/lib/statuses.js

@@ -0,0 +1,9 @@
+module.exports = {
+  1: 'ls', // WHATWG Living Standard
+  2: 'rec', // W3C Recommendation
+  3: 'pr', // W3C Proposed Recommendation
+  4: 'cr', // W3C Candidate Recommendation
+  5: 'wd', // W3C Working Draft
+  6: 'other', // Non-W3C, but reputable
+  7: 'unoff' // Unofficial, Editor's Draft or W3C "Note"
+}