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/@babel/plugin-transform-async-to-generator/README.md

@@ -0,0 +1,19 @@
+# @babel/plugin-transform-async-to-generator
+
+> Turn async functions into ES2015 generators
+
+See our website [@babel/plugin-transform-async-to-generator](https://babeljs.io/docs/babel-plugin-transform-async-to-generator) for more information.
+
+## Install
+
+Using npm:
+
+```sh
+npm install --save-dev @babel/plugin-transform-async-to-generator
+```
+
+or using yarn:
+
+```sh
+yarn add @babel/plugin-transform-async-to-generator --dev
+```