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/2022/TestIntegrityLevel.js

@@ -0,0 +1,40 @@
+'use strict';
+
+var $gOPD = require('gopd');
+var $TypeError = require('es-errors/type');
+
+var every = require('../helpers/every');
+var OwnPropertyKeys = require('own-keys');
+var isObject = require('es-object-atoms/isObject');
+
+var IsDataDescriptor = require('./IsDataDescriptor');
+var IsExtensible = require('./IsExtensible');
+var ToPropertyDescriptor = require('./ToPropertyDescriptor');
+
+// https://262.ecma-international.org/6.0/#sec-testintegritylevel
+
+module.exports = function TestIntegrityLevel(O, level) {
+	if (!isObject(O)) {
+		throw new $TypeError('Assertion failed: Type(O) is not Object');
+	}
+	if (level !== 'sealed' && level !== 'frozen') {
+		throw new $TypeError('Assertion failed: `level` must be `"sealed"` or `"frozen"`');
+	}
+	var status = IsExtensible(O);
+	if (status || !$gOPD) {
+		return false;
+	}
+	var theKeys = OwnPropertyKeys(O);
+	return theKeys.length === 0 || every(theKeys, function (k) {
+		var currentDesc = $gOPD(O, k);
+		if (typeof currentDesc !== 'undefined') {
+			if (currentDesc.configurable) {
+				return false;
+			}
+			if (level === 'frozen' && IsDataDescriptor(ToPropertyDescriptor(currentDesc)) && currentDesc.writable) {
+				return false;
+			}
+		}
+		return true;
+	});
+};