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/_cloneArrayBuffer.js

@@ -0,0 +1,16 @@
+var Uint8Array = require('./_Uint8Array');
+
+/**
+ * Creates a clone of `arrayBuffer`.
+ *
+ * @private
+ * @param {ArrayBuffer} arrayBuffer The array buffer to clone.
+ * @returns {ArrayBuffer} Returns the cloned array buffer.
+ */
+function cloneArrayBuffer(arrayBuffer) {
+  var result = new arrayBuffer.constructor(arrayBuffer.byteLength);
+  new Uint8Array(result).set(new Uint8Array(arrayBuffer));
+  return result;
+}
+
+module.exports = cloneArrayBuffer;