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/Sinhala.js

@@ -0,0 +1,3 @@
+const set = require('regenerate')(0xDBD, 0xDCA, 0xDD6, 0x1CF2);
+set.addRange(0x964, 0x965).addRange(0xD81, 0xD83).addRange(0xD85, 0xD96).addRange(0xD9A, 0xDB1).addRange(0xDB3, 0xDBB).addRange(0xDC0, 0xDC6).addRange(0xDCF, 0xDD4).addRange(0xDD8, 0xDDF).addRange(0xDE6, 0xDEF).addRange(0xDF2, 0xDF4).addRange(0x111E1, 0x111F4);
+exports.characters = set;