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/_baseIsSet.js

@@ -0,0 +1,18 @@
+var getTag = require('./_getTag'),
+    isObjectLike = require('./isObjectLike');
+
+/** `Object#toString` result references. */
+var setTag = '[object Set]';
+
+/**
+ * The base implementation of `_.isSet` without Node.js optimizations.
+ *
+ * @private
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is a set, else `false`.
+ */
+function baseIsSet(value) {
+  return isObjectLike(value) && getTag(value) == setTag;
+}
+
+module.exports = baseIsSet;