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/regenerate-unicode-properties/Script_Extensions/Vithkuqi.js

@@ -0,0 +1,3 @@
+const set = require('regenerate')();
+set.addRange(0x10570, 0x1057A).addRange(0x1057C, 0x1058A).addRange(0x1058C, 0x10592).addRange(0x10594, 0x10595).addRange(0x10597, 0x105A1).addRange(0x105A3, 0x105B1).addRange(0x105B3, 0x105B9).addRange(0x105BB, 0x105BC);
+exports.characters = set;