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/_MapCache.js

@@ -0,0 +1,32 @@
+var mapCacheClear = require('./_mapCacheClear'),
+    mapCacheDelete = require('./_mapCacheDelete'),
+    mapCacheGet = require('./_mapCacheGet'),
+    mapCacheHas = require('./_mapCacheHas'),
+    mapCacheSet = require('./_mapCacheSet');
+
+/**
+ * Creates a map cache object to store key-value pairs.
+ *
+ * @private
+ * @constructor
+ * @param {Array} [entries] The key-value pairs to cache.
+ */
+function MapCache(entries) {
+  var index = -1,
+      length = entries == null ? 0 : entries.length;
+
+  this.clear();
+  while (++index < length) {
+    var entry = entries[index];
+    this.set(entry[0], entry[1]);
+  }
+}
+
+// Add methods to `MapCache`.
+MapCache.prototype.clear = mapCacheClear;
+MapCache.prototype['delete'] = mapCacheDelete;
+MapCache.prototype.get = mapCacheGet;
+MapCache.prototype.has = mapCacheHas;
+MapCache.prototype.set = mapCacheSet;
+
+module.exports = MapCache;