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/Hiragana.js

@@ -0,0 +1,3 @@
+const set = require('regenerate')(0x3037, 0xFF70, 0x1B132, 0x1F200);
+set.addRange(0x3001, 0x3003).addRange(0x3008, 0x3011).addRange(0x3013, 0x301F).addRange(0x3030, 0x3035).addRange(0x303C, 0x303D).addRange(0x3041, 0x3096).addRange(0x3099, 0x30A0).addRange(0x30FB, 0x30FC).addRange(0xFE45, 0xFE46).addRange(0xFF61, 0xFF65).addRange(0xFF9E, 0xFF9F).addRange(0x1B001, 0x1B11F).addRange(0x1B150, 0x1B152);
+exports.characters = set;