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/Linear_B.js

@@ -0,0 +1,3 @@
+const set = require('regenerate')();
+set.addRange(0x10000, 0x1000B).addRange(0x1000D, 0x10026).addRange(0x10028, 0x1003A).addRange(0x1003C, 0x1003D).addRange(0x1003F, 0x1004D).addRange(0x10050, 0x1005D).addRange(0x10080, 0x100FA).addRange(0x10100, 0x10102).addRange(0x10107, 0x10133).addRange(0x10137, 0x1013F);
+exports.characters = set;