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/@jridgewell/trace-mapping/src/resolve.ts

@@ -0,0 +1,16 @@
+import resolveUri from '@jridgewell/resolve-uri';
+import stripFilename from './strip-filename';
+
+type Resolve = (source: string | null) => string;
+export default function resolver(
+  mapUrl: string | null | undefined,
+  sourceRoot: string | undefined,
+): Resolve {
+  const from = stripFilename(mapUrl);
+  // The sourceRoot is always treated as a directory, if it's not empty.
+  // https://github.com/mozilla/source-map/blob/8cb3ee57/lib/util.js#L327
+  // https://github.com/chromium/chromium/blob/da4adbb3/third_party/blink/renderer/devtools/front_end/sdk/SourceMap.js#L400-L401
+  const prefix = sourceRoot ? sourceRoot + '/' : '';
+
+  return (source) => resolveUri(prefix + (source || ''), from);
+}