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/_cloneSymbol.js

@@ -0,0 +1,18 @@
+var Symbol = require('./_Symbol');
+
+/** Used to convert symbols to primitives and strings. */
+var symbolProto = Symbol ? Symbol.prototype : undefined,
+    symbolValueOf = symbolProto ? symbolProto.valueOf : undefined;
+
+/**
+ * Creates a clone of the `symbol` object.
+ *
+ * @private
+ * @param {Object} symbol The symbol object to clone.
+ * @returns {Object} Returns the cloned symbol object.
+ */
+function cloneSymbol(symbol) {
+  return symbolValueOf ? Object(symbolValueOf.call(symbol)) : {};
+}
+
+module.exports = cloneSymbol;