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/defineEnumerableProperties.js

@@ -0,0 +1,12 @@
+function _defineEnumerableProperties(e, r) {
+  for (var t in r) {
+    var n = r[t];
+    n.configurable = n.enumerable = !0, "value" in n && (n.writable = !0), Object.defineProperty(e, t, n);
+  }
+  if (Object.getOwnPropertySymbols) for (var a = Object.getOwnPropertySymbols(r), b = 0; b < a.length; b++) {
+    var i = a[b];
+    (n = r[i]).configurable = n.enumerable = !0, "value" in n && (n.writable = !0), Object.defineProperty(e, i, n);
+  }
+  return e;
+}
+module.exports = _defineEnumerableProperties, module.exports.__esModule = true, module.exports["default"] = module.exports;