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/_toSource.js

@@ -0,0 +1,26 @@
+/** Used for built-in method references. */
+var funcProto = Function.prototype;
+
+/** Used to resolve the decompiled source of functions. */
+var funcToString = funcProto.toString;
+
+/**
+ * Converts `func` to its source code.
+ *
+ * @private
+ * @param {Function} func The function to convert.
+ * @returns {string} Returns the source code.
+ */
+function toSource(func) {
+  if (func != null) {
+    try {
+      return funcToString.call(func);
+    } catch (e) {}
+    try {
+      return (func + '');
+    } catch (e) {}
+  }
+  return '';
+}
+
+module.exports = toSource;