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/vite/README.md

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+# vite ⚡
+
+> Next Generation Frontend Tooling
+
+- 💡 Instant Server Start
+- ⚡️ Lightning Fast HMR
+- 🛠️ Rich Features
+- 📦 Optimized Build
+- 🔩 Universal Plugin Interface
+- 🔑 Fully Typed APIs
+
+Vite (French word for "fast", pronounced `/vit/`) is a new breed of frontend build tool that significantly improves the frontend development experience. It consists of two major parts:
+
+- A dev server that serves your source files over [native ES modules](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules), with [rich built-in features](https://vite.dev/guide/features.html) and astonishingly fast [Hot Module Replacement (HMR)](https://vite.dev/guide/features.html#hot-module-replacement).
+
+- A [build command](https://vite.dev/guide/build.html) that bundles your code with [Rollup](https://rollupjs.org), pre-configured to output highly optimized static assets for production.
+
+In addition, Vite is highly extensible via its [Plugin API](https://vite.dev/guide/api-plugin.html) and [JavaScript API](https://vite.dev/guide/api-javascript.html) with full typing support.
+
+[Read the Docs to Learn More](https://vite.dev).