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/2020/ToPropertyDescriptor.js

@@ -0,0 +1,50 @@
+'use strict';
+
+var hasOwn = require('hasown');
+
+var $TypeError = require('es-errors/type');
+var isObject = require('es-object-atoms/isObject');
+
+var IsCallable = require('./IsCallable');
+var ToBoolean = require('./ToBoolean');
+
+// https://262.ecma-international.org/5.1/#sec-8.10.5
+
+module.exports = function ToPropertyDescriptor(Obj) {
+	if (!isObject(Obj)) {
+		throw new $TypeError('ToPropertyDescriptor requires an object');
+	}
+
+	var desc = {};
+	if (hasOwn(Obj, 'enumerable')) {
+		desc['[[Enumerable]]'] = ToBoolean(Obj.enumerable);
+	}
+	if (hasOwn(Obj, 'configurable')) {
+		desc['[[Configurable]]'] = ToBoolean(Obj.configurable);
+	}
+	if (hasOwn(Obj, 'value')) {
+		desc['[[Value]]'] = Obj.value;
+	}
+	if (hasOwn(Obj, 'writable')) {
+		desc['[[Writable]]'] = ToBoolean(Obj.writable);
+	}
+	if (hasOwn(Obj, 'get')) {
+		var getter = Obj.get;
+		if (typeof getter !== 'undefined' && !IsCallable(getter)) {
+			throw new $TypeError('getter must be a function');
+		}
+		desc['[[Get]]'] = getter;
+	}
+	if (hasOwn(Obj, 'set')) {
+		var setter = Obj.set;
+		if (typeof setter !== 'undefined' && !IsCallable(setter)) {
+			throw new $TypeError('setter must be a function');
+		}
+		desc['[[Set]]'] = setter;
+	}
+
+	if ((hasOwn(desc, '[[Get]]') || hasOwn(desc, '[[Set]]')) && (hasOwn(desc, '[[Value]]') || hasOwn(desc, '[[Writable]]'))) {
+		throw new $TypeError('Invalid property descriptor. Cannot both specify accessors and a value or writable attribute');
+	}
+	return desc;
+};