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/_trimmedEndIndex.js

@@ -0,0 +1,19 @@
+/** Used to match a single whitespace character. */
+var reWhitespace = /\s/;
+
+/**
+ * Used by `_.trim` and `_.trimEnd` to get the index of the last non-whitespace
+ * character of `string`.
+ *
+ * @private
+ * @param {string} string The string to inspect.
+ * @returns {number} Returns the index of the last non-whitespace character.
+ */
+function trimmedEndIndex(string) {
+  var index = string.length;
+
+  while (index-- && reWhitespace.test(string.charAt(index))) {}
+  return index;
+}
+
+module.exports = trimmedEndIndex;