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/lodash/math.js

@@ -0,0 +1,17 @@
+module.exports = {
+  'add': require('./add'),
+  'ceil': require('./ceil'),
+  'divide': require('./divide'),
+  'floor': require('./floor'),
+  'max': require('./max'),
+  'maxBy': require('./maxBy'),
+  'mean': require('./mean'),
+  'meanBy': require('./meanBy'),
+  'min': require('./min'),
+  'minBy': require('./minBy'),
+  'multiply': require('./multiply'),
+  'round': require('./round'),
+  'subtract': require('./subtract'),
+  'sum': require('./sum'),
+  'sumBy': require('./sumBy')
+};