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-abstract/2021/TimeClip.js

@@ -0,0 +1,20 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var $Date = GetIntrinsic('%Date%');
+
+var $isFinite = require('math-intrinsics/isFinite');
+var abs = require('math-intrinsics/abs');
+
+var ToNumber = require('./ToNumber');
+
+// https://262.ecma-international.org/5.1/#sec-15.9.1.14
+
+module.exports = function TimeClip(time) {
+	if (!$isFinite(time) || abs(time) > 8.64e15) {
+		return NaN;
+	}
+	return +new $Date(ToNumber(time));
+};
+