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/workbox-cacheable-response/build/workbox-cacheable-response.prod.js

@@ -0,0 +1,2 @@
+this.workbox=this.workbox||{},this.workbox.cacheableResponse=function(s){"use strict";try{self["workbox:cacheable-response:7.3.0"]&&_()}catch(s){}class t{constructor(s={}){this.ss=s.statuses,this.ts=s.headers}isResponseCacheable(s){let t=!0;return this.ss&&(t=this.ss.includes(s.status)),this.ts&&t&&(t=Object.keys(this.ts).some((t=>s.headers.get(t)===this.ts[t]))),t}}return s.CacheableResponse=t,s.CacheableResponsePlugin=class{constructor(s){this.cacheWillUpdate=async({response:s})=>this.hs.isResponseCacheable(s)?s:null,this.hs=new t(s)}},s}({});
+//# sourceMappingURL=workbox-cacheable-response.prod.js.map