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/vitest/dist/browser.js

@@ -0,0 +1,9 @@
+export { g as getCoverageProvider, s as startCoverageInsideWorker, a as stopCoverageInsideWorker, t as takeCoverageInsideWorker } from './chunks/coverage.BoMDb1ip.js';
+export { s as SpyModule } from './chunks/spy.Cf_4R5Oe.js';
+export { l as loadDiffConfig, a as loadSnapshotSerializers, s as setupCommonEnv } from './chunks/setup-common.Dj6BZI3u.js';
+export { collectTests, processError, startTests } from '@vitest/runner';
+import '@vitest/spy';
+import '@vitest/snapshot';
+import '@vitest/utils';
+import './chunks/run-once.2ogXb3JV.js';
+import './chunks/utils.C8RiOc4B.js';