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/_nativeKeysIn.js

@@ -0,0 +1,20 @@
+/**
+ * This function is like
+ * [`Object.keys`](http://ecma-international.org/ecma-262/7.0/#sec-object.keys)
+ * except that it includes inherited enumerable properties.
+ *
+ * @private
+ * @param {Object} object The object to query.
+ * @returns {Array} Returns the array of property names.
+ */
+function nativeKeysIn(object) {
+  var result = [];
+  if (object != null) {
+    for (var key in Object(object)) {
+      result.push(key);
+    }
+  }
+  return result;
+}
+
+module.exports = nativeKeysIn;