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/_isMasked.js

@@ -0,0 +1,20 @@
+var coreJsData = require('./_coreJsData');
+
+/** Used to detect methods masquerading as native. */
+var maskSrcKey = (function() {
+  var uid = /[^.]+$/.exec(coreJsData && coreJsData.keys && coreJsData.keys.IE_PROTO || '');
+  return uid ? ('Symbol(src)_1.' + uid) : '';
+}());
+
+/**
+ * Checks if `func` has its source masked.
+ *
+ * @private
+ * @param {Function} func The function to check.
+ * @returns {boolean} Returns `true` if `func` is masked, else `false`.
+ */
+function isMasked(func) {
+  return !!maskSrcKey && (maskSrcKey in func);
+}
+
+module.exports = isMasked;