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/lodash/_hashSet.js

@@ -0,0 +1,23 @@
+var nativeCreate = require('./_nativeCreate');
+
+/** Used to stand-in for `undefined` hash values. */
+var HASH_UNDEFINED = '__lodash_hash_undefined__';
+
+/**
+ * Sets the hash `key` to `value`.
+ *
+ * @private
+ * @name set
+ * @memberOf Hash
+ * @param {string} key The key of the value to set.
+ * @param {*} value The value to set.
+ * @returns {Object} Returns the hash instance.
+ */
+function hashSet(key, value) {
+  var data = this.__data__;
+  this.size += this.has(key) ? 0 : 1;
+  data[key] = (nativeCreate && value === undefined) ? HASH_UNDEFINED : value;
+  return this;
+}
+
+module.exports = hashSet;