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-broadcast-update/build/workbox-broadcast-update.prod.js

@@ -0,0 +1,2 @@
+this.workbox=this.workbox||{},this.workbox.broadcastUpdate=function(t,s,a,e){"use strict";try{self["workbox:broadcast-update:7.3.0"]&&_()}catch(t){}const n=(t,s,a)=>!a.some((a=>t.headers.has(a)&&s.headers.has(a)))||a.every((a=>{const e=t.headers.has(a)===s.headers.has(a),n=t.headers.get(a)===s.headers.get(a);return e&&n})),i=["content-length","etag","last-modified"],o=/^((?!chrome|android).)*safari/i.test(navigator.userAgent);function c(t){return{cacheName:t.cacheName,updatedURL:t.request.url}}class r{constructor({generatePayload:t,headersToCheck:s,notifyAllClients:a}={}){this.ht=s||i,this.ft=t||c,this.lt=null==a||a}async notifyIfUpdated(t){if(t.oldResponse&&!n(t.oldResponse,t.newResponse,this.ht)){const e={type:"CACHE_UPDATED",meta:"workbox-broadcast-update",payload:this.ft(t)};if("navigate"===t.request.mode){let e;t.event instanceof FetchEvent&&(e=t.event.resultingClientId);await a.resultingClientExists(e)&&!o||await s.timeout(3500)}if(this.lt){const t=await self.clients.matchAll({type:"window"});for(const s of t)s.postMessage(e)}else if(t.event instanceof FetchEvent){const s=await self.clients.get(t.event.clientId);null==s||s.postMessage(e)}}}}return t.BroadcastCacheUpdate=r,t.BroadcastUpdatePlugin=class{constructor(t){this.cacheDidUpdate=async t=>{e.dontWaitFor(this.dt.notifyIfUpdated(t))},this.dt=new r(t)}},t.responsesAreSame=n,t}({},workbox.core._private,workbox.core._private,workbox.core._private);
+//# sourceMappingURL=workbox-broadcast-update.prod.js.map