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/graceful-fs/clone.js

@@ -0,0 +1,23 @@
+'use strict'
+
+module.exports = clone
+
+var getPrototypeOf = Object.getPrototypeOf || function (obj) {
+  return obj.__proto__
+}
+
+function clone (obj) {
+  if (obj === null || typeof obj !== 'object')
+    return obj
+
+  if (obj instanceof Object)
+    var copy = { __proto__: getPrototypeOf(obj) }
+  else
+    var copy = Object.create(null)
+
+  Object.getOwnPropertyNames(obj).forEach(function (key) {
+    Object.defineProperty(copy, key, Object.getOwnPropertyDescriptor(obj, key))
+  })
+
+  return copy
+}