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/workbox-precaching/utils/createCacheKey.d.ts

@@ -0,0 +1,17 @@
+import { PrecacheEntry } from '../_types.js';
+import '../_version.js';
+interface CacheKey {
+    cacheKey: string;
+    url: string;
+}
+/**
+ * Converts a manifest entry into a versioned URL suitable for precaching.
+ *
+ * @param {Object|string} entry
+ * @return {string} A URL with versioning info.
+ *
+ * @private
+ * @memberof workbox-precaching
+ */
+export declare function createCacheKey(entry: PrecacheEntry | string): CacheKey;
+export {};