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/meanBy.js

@@ -0,0 +1,31 @@
+var baseIteratee = require('./_baseIteratee'),
+    baseMean = require('./_baseMean');
+
+/**
+ * This method is like `_.mean` except that it accepts `iteratee` which is
+ * invoked for each element in `array` to generate the value to be averaged.
+ * The iteratee is invoked with one argument: (value).
+ *
+ * @static
+ * @memberOf _
+ * @since 4.7.0
+ * @category Math
+ * @param {Array} array The array to iterate over.
+ * @param {Function} [iteratee=_.identity] The iteratee invoked per element.
+ * @returns {number} Returns the mean.
+ * @example
+ *
+ * var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];
+ *
+ * _.meanBy(objects, function(o) { return o.n; });
+ * // => 5
+ *
+ * // The `_.property` iteratee shorthand.
+ * _.meanBy(objects, 'n');
+ * // => 5
+ */
+function meanBy(array, iteratee) {
+  return baseMean(array, baseIteratee(iteratee, 2));
+}
+
+module.exports = meanBy;