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/@babel/runtime/helpers/esm/using.js

@@ -0,0 +1,12 @@
+function _using(o, n, e) {
+  if (null == n) return n;
+  if (Object(n) !== n) throw new TypeError("using declarations can only be used with objects, functions, null, or undefined.");
+  if (e) var r = n[Symbol.asyncDispose || Symbol["for"]("Symbol.asyncDispose")];
+  if (null == r && (r = n[Symbol.dispose || Symbol["for"]("Symbol.dispose")]), "function" != typeof r) throw new TypeError("Property [Symbol.dispose] is not a function.");
+  return o.push({
+    v: n,
+    d: r,
+    a: e
+  }), n;
+}
+export { _using as default };