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/flatMapDepth.js

@@ -0,0 +1,31 @@
+var baseFlatten = require('./_baseFlatten'),
+    map = require('./map'),
+    toInteger = require('./toInteger');
+
+/**
+ * This method is like `_.flatMap` except that it recursively flattens the
+ * mapped results up to `depth` times.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.7.0
+ * @category Collection
+ * @param {Array|Object} collection The collection to iterate over.
+ * @param {Function} [iteratee=_.identity] The function invoked per iteration.
+ * @param {number} [depth=1] The maximum recursion depth.
+ * @returns {Array} Returns the new flattened array.
+ * @example
+ *
+ * function duplicate(n) {
+ *   return [[[n, n]]];
+ * }
+ *
+ * _.flatMapDepth([1, 2], duplicate, 2);
+ * // => [[1, 1], [2, 2]]
+ */
+function flatMapDepth(collection, iteratee, depth) {
+  depth = depth === undefined ? 1 : toInteger(depth);
+  return baseFlatten(map(collection, iteratee), depth);
+}
+
+module.exports = flatMapDepth;