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/which-collection/index.d.ts

@@ -0,0 +1,13 @@
+/**
+ * Determines the type of the given collection, or returns false.
+ *
+ * @param {unknown} value The potential collection
+ * @returns {'Map' | 'Set' | 'WeakMap' | 'WeakSet' | false} 'Map' | 'Set' | 'WeakMap' | 'WeakSet' | false
+ */
+declare function whichCollection<K, V>(value: Map<K, V>): 'Map';
+declare function whichCollection<T>(value: Set<T>): 'Set';
+declare function whichCollection<K extends WeakKey, V>(value: WeakMap<K, V>): 'WeakMap';
+declare function whichCollection<T extends WeakKey>(value: WeakSet<T>): 'WeakSet';
+declare function whichCollection(value: null | undefined | boolean | number | bigint | symbol | unknown): false;
+
+export = whichCollection;