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/preset-env/lib/polyfills/utils.cjs

@@ -0,0 +1,21 @@
+exports.getImportSource = function ({
+  node
+}) {
+  if (node.specifiers.length === 0) return node.source.value;
+};
+exports.getRequireSource = function ({
+  node
+}) {
+  if (node.type !== "ExpressionStatement") return;
+  const {
+    expression
+  } = node;
+  if (expression.type === "CallExpression" && expression.callee.type === "Identifier" && expression.callee.name === "require" && expression.arguments.length === 1 && expression.arguments[0].type === "StringLiteral") {
+    return expression.arguments[0].value;
+  }
+};
+exports.isPolyfillSource = function (source) {
+  return source === "@babel/polyfill" || source === "core-js";
+};
+
+//# sourceMappingURL=utils.cjs.map