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/PrecacheInstallReportPlugin.d.ts

@@ -0,0 +1,15 @@
+import { WorkboxPlugin } from 'workbox-core/types.js';
+import '../_version.js';
+/**
+ * A plugin, designed to be used with PrecacheController, to determine the
+ * of assets that were updated (or not updated) during the install event.
+ *
+ * @private
+ */
+declare class PrecacheInstallReportPlugin implements WorkboxPlugin {
+    updatedURLs: string[];
+    notUpdatedURLs: string[];
+    handlerWillStart: WorkboxPlugin['handlerWillStart'];
+    cachedResponseWillBeUsed: WorkboxPlugin['cachedResponseWillBeUsed'];
+}
+export { PrecacheInstallReportPlugin };