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/tsx/README.md

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+<h1 align="center">
+<br>
+<picture>
+	<source media="(prefers-color-scheme: dark)" srcset=".github/logo-dark.svg">
+	<img width="160" alt="tsx" src=".github/logo-light.svg">
+</picture>
+<br><br>
+<a href="https://npm.im/tsx"><img src="https://badgen.net/npm/v/tsx"></a> <a href="https://npm.im/tsx"><img src="https://badgen.net/npm/dm/tsx"></a>
+</h1>
+
+<p align="center">
+TypeScript Execute (tsx): The easiest way to run TypeScript in Node.js
+<br><br>
+<a href="https://tsx.is">Documentation</a>&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;&nbsp;&nbsp;&nbsp;<a href="https://tsx.is/getting-started">Getting started →</a>
+</p>
+
+<br>
+
+<p align="center">
+	<a href="https://github.com/sponsors/privatenumber/sponsorships?tier_id=398771"><img width="412" src="https://raw.githubusercontent.com/privatenumber/sponsors/master/banners/assets/donate.webp"></a>
+	<a href="https://github.com/sponsors/privatenumber/sponsorships?tier_id=416984"><img width="412" src="https://raw.githubusercontent.com/privatenumber/sponsors/master/banners/assets/sponsor.webp"></a>
+</p>
+<p align="center"><sup><i>Already a sponsor?</i> Join the discussion in the <a href="https://github.com/pvtnbr/tsx">Development repo</a>!</sup></p>
+
+## Sponsors
+
+<p align="center">
+	<a href="https://github.com/sponsors/privatenumber">
+		<img src="https://cdn.jsdelivr.net/gh/privatenumber/sponsors/sponsorkit/sponsors.svg">
+	</a>
+</p>
+