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/siginfo/index.js

@@ -0,0 +1,20 @@
+module.exports = function (query, force) {
+  var isAttached = false
+  if (process.stderr.isTTY || force === true) {
+    isAttached = true
+    process.on('SIGINFO', onsiginfo)
+    process.on('SIGUSR1', onsiginfo)
+  }
+
+  return function () {
+    if (isAttached === true) {
+      process.removeListener('SIGINFO', onsiginfo)
+      process.removeListener('SIGUSR1', onsiginfo)
+      isAttached = false
+    }
+  }
+
+  function onsiginfo () {
+    query()
+  }
+}