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/_isMaskable.js

@@ -0,0 +1,14 @@
+var coreJsData = require('./_coreJsData'),
+    isFunction = require('./isFunction'),
+    stubFalse = require('./stubFalse');
+
+/**
+ * Checks if `func` is capable of being masked.
+ *
+ * @private
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `func` is maskable, else `false`.
+ */
+var isMaskable = coreJsData ? isFunction : stubFalse;
+
+module.exports = isMaskable;