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/2023/GetOwnPropertyKeys.js

@@ -0,0 +1,30 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var hasSymbols = require('has-symbols')();
+
+var $TypeError = require('es-errors/type');
+var isObject = require('es-object-atoms/isObject');
+
+var $gOPN = GetIntrinsic('%Object.getOwnPropertyNames%', true);
+var $gOPS = hasSymbols && GetIntrinsic('%Object.getOwnPropertySymbols%', true);
+var keys = require('object-keys');
+
+// https://262.ecma-international.org/6.0/#sec-getownpropertykeys
+
+module.exports = function GetOwnPropertyKeys(O, Type) {
+	if (!isObject(O)) {
+		throw new $TypeError('Assertion failed: Type(O) is not Object');
+	}
+	if (Type === 'Symbol') {
+		return $gOPS ? $gOPS(O) : [];
+	}
+	if (Type === 'String') {
+		if (!$gOPN) {
+			return keys(O);
+		}
+		return $gOPN(O);
+	}
+	throw new $TypeError('Assertion failed: `Type` must be `"String"` or `"Symbol"`');
+};