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/_SetCache.js

@@ -0,0 +1,27 @@
+var MapCache = require('./_MapCache'),
+    setCacheAdd = require('./_setCacheAdd'),
+    setCacheHas = require('./_setCacheHas');
+
+/**
+ *
+ * Creates an array cache object to store unique values.
+ *
+ * @private
+ * @constructor
+ * @param {Array} [values] The values to cache.
+ */
+function SetCache(values) {
+  var index = -1,
+      length = values == null ? 0 : values.length;
+
+  this.__data__ = new MapCache;
+  while (++index < length) {
+    this.add(values[index]);
+  }
+}
+
+// Add methods to `SetCache`.
+SetCache.prototype.add = SetCache.prototype.push = setCacheAdd;
+SetCache.prototype.has = setCacheHas;
+
+module.exports = SetCache;