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/2018/SplitMatch.js

@@ -0,0 +1,35 @@
+'use strict';
+
+var callBound = require('call-bound');
+
+var $TypeError = require('es-errors/type');
+var isInteger = require('math-intrinsics/isInteger');
+
+var $charAt = callBound('String.prototype.charAt');
+
+// https://262.ecma-international.org/6.0/#sec-splitmatch
+
+module.exports = function SplitMatch(S, q, R) {
+	if (typeof S !== 'string') {
+		throw new $TypeError('Assertion failed: `S` must be a String');
+	}
+	if (!isInteger(q)) {
+		throw new $TypeError('Assertion failed: `q` must be an integer');
+	}
+	if (typeof R !== 'string') {
+		throw new $TypeError('Assertion failed: `R` must be a String');
+	}
+	var r = R.length;
+	var s = S.length;
+	if (q + r > s) {
+		return false;
+	}
+
+	for (var i = 0; i < r; i += 1) {
+		if ($charAt(S, q + i) !== $charAt(R, i)) {
+			return false;
+		}
+	}
+
+	return q + r;
+};