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/helpers/assertRecord.js

@@ -0,0 +1,32 @@
+'use strict';
+
+// TODO, semver-major: delete this
+
+var $TypeError = require('es-errors/type');
+var $SyntaxError = require('es-errors/syntax');
+
+var isMatchRecord = require('./records/match-record');
+var isPropertyDescriptor = require('./records/property-descriptor');
+var isIteratorRecord = require('./records/iterator-record-2023');
+var isPromiseCapabilityRecord = require('./records/promise-capability-record');
+var isAsyncGeneratorRequestRecord = require('./records/async-generator-request-record');
+var isRegExpRecord = require('./records/regexp-record');
+
+var predicates = {
+	'Property Descriptor': isPropertyDescriptor,
+	'Match Record': isMatchRecord,
+	'Iterator Record': isIteratorRecord,
+	'PromiseCapability Record': isPromiseCapabilityRecord,
+	'AsyncGeneratorRequest Record': isAsyncGeneratorRequestRecord,
+	'RegExp Record': isRegExpRecord
+};
+
+module.exports = function assertRecord(Type, recordType, argumentName, value) {
+	var predicate = predicates[recordType];
+	if (typeof predicate !== 'function') {
+		throw new $SyntaxError('unknown record type: ' + recordType);
+	}
+	if (!predicate(value)) {
+		throw new $TypeError(argumentName + ' must be a ' + recordType);
+	}
+};