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/2025/AddValueToKeyedGroup.js

@@ -0,0 +1,45 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var SameValue = require('./SameValue');
+
+var IsArray = require('../helpers/IsArray');
+var every = require('../helpers/every');
+var forEach = require('../helpers/forEach');
+
+var hasOwn = require('hasown');
+
+var isKeyedGroup = function (group) {
+	return hasOwn(group, '[[Key]]')
+        && hasOwn(group, '[[Elements]]')
+        && IsArray(group['[[Elements]]']);
+};
+
+// https://262.ecma-international.org/15.0/#sec-add-value-to-keyed-group
+
+module.exports = function AddValueToKeyedGroup(groups, key, value) {
+	if (!IsArray(groups) || (groups.length > 0 && !every(groups, isKeyedGroup))) {
+		throw new $TypeError('Assertion failed: `groups` must be a List of Records with [[Key]] and [[Elements]]');
+	}
+
+	var matched = 0;
+	forEach(groups, function (g) { // step 1
+		if (SameValue(g['[[Key]]'], key)) { // step 2
+			matched += 1;
+			if (matched > 1) {
+				throw new $TypeError('Assertion failed: Exactly one element of groups meets this criterion'); // step 2.a
+			}
+
+			var arr = g['[[Elements]]'];
+			arr[arr.length] = value; // step 2.b
+		}
+	});
+
+	if (matched === 0) {
+		var group = { '[[Key]]': key, '[[Elements]]': [value] }; // step 2
+
+		// eslint-disable-next-line no-param-reassign
+		groups[groups.length] = group; // step 3
+	}
+};