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/_isKey.js

@@ -0,0 +1,29 @@
+var isArray = require('./isArray'),
+    isSymbol = require('./isSymbol');
+
+/** Used to match property names within property paths. */
+var reIsDeepProp = /\.|\[(?:[^[\]]*|(["'])(?:(?!\1)[^\\]|\\.)*?\1)\]/,
+    reIsPlainProp = /^\w*$/;
+
+/**
+ * Checks if `value` is a property name and not a property path.
+ *
+ * @private
+ * @param {*} value The value to check.
+ * @param {Object} [object] The object to query keys on.
+ * @returns {boolean} Returns `true` if `value` is a property name, else `false`.
+ */
+function isKey(value, object) {
+  if (isArray(value)) {
+    return false;
+  }
+  var type = typeof value;
+  if (type == 'number' || type == 'symbol' || type == 'boolean' ||
+      value == null || isSymbol(value)) {
+    return true;
+  }
+  return reIsPlainProp.test(value) || !reIsDeepProp.test(value) ||
+    (object != null && value in Object(object));
+}
+
+module.exports = isKey;