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/async/internal/wrapAsync.js

@@ -0,0 +1,34 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+exports.isAsyncIterable = exports.isAsyncGenerator = exports.isAsync = undefined;
+
+var _asyncify = require('../asyncify.js');
+
+var _asyncify2 = _interopRequireDefault(_asyncify);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+function isAsync(fn) {
+    return fn[Symbol.toStringTag] === 'AsyncFunction';
+}
+
+function isAsyncGenerator(fn) {
+    return fn[Symbol.toStringTag] === 'AsyncGenerator';
+}
+
+function isAsyncIterable(obj) {
+    return typeof obj[Symbol.asyncIterator] === 'function';
+}
+
+function wrapAsync(asyncFn) {
+    if (typeof asyncFn !== 'function') throw new Error('expected a function');
+    return isAsync(asyncFn) ? (0, _asyncify2.default)(asyncFn) : asyncFn;
+}
+
+exports.default = wrapAsync;
+exports.isAsync = isAsync;
+exports.isAsyncGenerator = isAsyncGenerator;
+exports.isAsyncIterable = isAsyncIterable;