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/caniuse-lite/dist/unpacker/region.js

@@ -0,0 +1,22 @@
+'use strict'
+
+const browsers = require('./browsers').browsers
+
+function unpackRegion(packed) {
+  return Object.keys(packed).reduce((list, browser) => {
+    let data = packed[browser]
+    list[browsers[browser]] = Object.keys(data).reduce((memo, key) => {
+      let stats = data[key]
+      if (key === '_') {
+        stats.split(' ').forEach(version => (memo[version] = null))
+      } else {
+        memo[key] = stats
+      }
+      return memo
+    }, {})
+    return list
+  }, {})
+}
+
+module.exports = unpackRegion
+module.exports.default = unpackRegion