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/path-key/index.js

@@ -0,0 +1,16 @@
+'use strict';
+
+const pathKey = (options = {}) => {
+	const environment = options.env || process.env;
+	const platform = options.platform || process.platform;
+
+	if (platform !== 'win32') {
+		return 'PATH';
+	}
+
+	return Object.keys(environment).reverse().find(key => key.toUpperCase() === 'PATH') || 'Path';
+};
+
+module.exports = pathKey;
+// TODO: Remove this for the next major release
+module.exports.default = pathKey;