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/2024/GetStringIndex.js

@@ -0,0 +1,27 @@
+'use strict';
+
+var callBound = require('call-bound');
+var $TypeError = require('es-errors/type');
+var isInteger = require('math-intrinsics/isInteger');
+
+var StringToCodePoints = require('./StringToCodePoints');
+
+var $indexOf = callBound('String.prototype.indexOf');
+
+// https://262.ecma-international.org/13.0/#sec-getstringindex
+
+module.exports = function GetStringIndex(S, e) {
+	if (typeof S !== 'string') {
+		throw new $TypeError('Assertion failed: `S` must be a String');
+	}
+	if (!isInteger(e) || e < 0) {
+		throw new $TypeError('Assertion failed: `e` must be a non-negative integer');
+	}
+
+	if (S === '') {
+		return 0;
+	}
+	var codepoints = StringToCodePoints(S);
+	var eUTF = e >= codepoints.length ? S.length : $indexOf(S, codepoints[e]);
+	return eUTF;
+};