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/es-define-property/index.js

@@ -0,0 +1,14 @@
+'use strict';
+
+/** @type {import('.')} */
+var $defineProperty = Object.defineProperty || false;
+if ($defineProperty) {
+	try {
+		$defineProperty({}, 'a', { value: 1 });
+	} catch (e) {
+		// IE 8 has a broken defineProperty
+		$defineProperty = false;
+	}
+}
+
+module.exports = $defineProperty;