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/jsonfile/utils.js

@@ -0,0 +1,14 @@
+function stringify (obj, { EOL = '\n', finalEOL = true, replacer = null, spaces } = {}) {
+  const EOF = finalEOL ? EOL : ''
+  const str = JSON.stringify(obj, replacer, spaces)
+
+  return str.replace(/\n/g, EOL) + EOF
+}
+
+function stripBom (content) {
+  // we do this because JSON.parse would convert it to a utf8 string if encoding wasn't specified
+  if (Buffer.isBuffer(content)) content = content.toString('utf8')
+  return content.replace(/^\uFEFF/, '')
+}
+
+module.exports = { stringify, stripBom }