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/race.js

@@ -0,0 +1,67 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+
+var _once = require('./internal/once.js');
+
+var _once2 = _interopRequireDefault(_once);
+
+var _wrapAsync = require('./internal/wrapAsync.js');
+
+var _wrapAsync2 = _interopRequireDefault(_wrapAsync);
+
+var _awaitify = require('./internal/awaitify.js');
+
+var _awaitify2 = _interopRequireDefault(_awaitify);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+/**
+ * Runs the `tasks` array of functions in parallel, without waiting until the
+ * previous function has completed. Once any of the `tasks` complete or pass an
+ * error to its callback, the main `callback` is immediately called. It's
+ * equivalent to `Promise.race()`.
+ *
+ * @name race
+ * @static
+ * @memberOf module:ControlFlow
+ * @method
+ * @category Control Flow
+ * @param {Array} tasks - An array containing [async functions]{@link AsyncFunction}
+ * to run. Each function can complete with an optional `result` value.
+ * @param {Function} callback - A callback to run once any of the functions have
+ * completed. This function gets an error or result from the first function that
+ * completed. Invoked with (err, result).
+ * @returns {Promise} a promise, if a callback is omitted
+ * @example
+ *
+ * async.race([
+ *     function(callback) {
+ *         setTimeout(function() {
+ *             callback(null, 'one');
+ *         }, 200);
+ *     },
+ *     function(callback) {
+ *         setTimeout(function() {
+ *             callback(null, 'two');
+ *         }, 100);
+ *     }
+ * ],
+ * // main callback
+ * function(err, result) {
+ *     // the result will be equal to 'two' as it finishes earlier
+ * });
+ */
+function race(tasks, callback) {
+    callback = (0, _once2.default)(callback);
+    if (!Array.isArray(tasks)) return callback(new TypeError('First argument to race must be an array of functions'));
+    if (!tasks.length) return callback();
+    for (var i = 0, l = tasks.length; i < l; i++) {
+        (0, _wrapAsync2.default)(tasks[i])(callback);
+    }
+}
+
+exports.default = (0, _awaitify2.default)(race, 2);
+module.exports = exports.default;