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/2020/RegExpCreate.js

@@ -0,0 +1,21 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var $RegExp = GetIntrinsic('%RegExp%');
+
+// var RegExpAlloc = require('./RegExpAlloc');
+// var RegExpInitialize = require('./RegExpInitialize');
+var ToString = require('./ToString');
+
+// https://262.ecma-international.org/6.0/#sec-regexpcreate
+
+module.exports = function RegExpCreate(P, F) {
+	// var obj = RegExpAlloc($RegExp);
+	// return RegExpInitialize(obj, P, F);
+
+	// covers spec mechanics; bypass regex brand checking
+	var pattern = typeof P === 'undefined' ? '' : ToString(P);
+	var flags = typeof F === 'undefined' ? '' : ToString(F);
+	return new $RegExp(pattern, flags);
+};