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/2019/Set.js

@@ -0,0 +1,45 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+var isObject = require('es-object-atoms/isObject');
+
+var isPropertyKey = require('../helpers/isPropertyKey');
+var SameValue = require('./SameValue');
+
+// IE 9 does not throw in strict mode when writability/configurability/extensibility is violated
+var noThrowOnStrictViolation = (function () {
+	try {
+		delete [].length;
+		return true;
+	} catch (e) {
+		return false;
+	}
+}());
+
+// https://262.ecma-international.org/6.0/#sec-set-o-p-v-throw
+
+module.exports = function Set(O, P, V, Throw) {
+	if (!isObject(O)) {
+		throw new $TypeError('Assertion failed: `O` must be an Object');
+	}
+	if (!isPropertyKey(P)) {
+		throw new $TypeError('Assertion failed: `P` must be a Property Key');
+	}
+	if (typeof Throw !== 'boolean') {
+		throw new $TypeError('Assertion failed: `Throw` must be a Boolean');
+	}
+	if (Throw) {
+		O[P] = V; // eslint-disable-line no-param-reassign
+		if (noThrowOnStrictViolation && !SameValue(O[P], V)) {
+			throw new $TypeError('Attempted to assign to readonly property.');
+		}
+		return true;
+	}
+	try {
+		O[P] = V; // eslint-disable-line no-param-reassign
+		return noThrowOnStrictViolation ? SameValue(O[P], V) : true;
+	} catch (e) {
+		return false;
+	}
+
+};