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/is-async-function/index.js

@@ -0,0 +1,32 @@
+'use strict';
+
+var callBound = require('call-bound');
+var safeRegexTest = require('safe-regex-test');
+
+var toStr = callBound('Object.prototype.toString');
+var fnToStr = callBound('Function.prototype.toString');
+var isFnRegex = safeRegexTest(/^\s*async(?:\s+function(?:\s+|\()|\s*\()/);
+
+var hasToStringTag = require('has-tostringtag/shams')();
+var getProto = require('get-proto');
+
+var getAsyncFunc = require('async-function');
+
+/** @type {import('.')} */
+module.exports = function isAsyncFunction(fn) {
+	if (typeof fn !== 'function') {
+		return false;
+	}
+	if (isFnRegex(fnToStr(fn))) {
+		return true;
+	}
+	if (!hasToStringTag) {
+		var str = toStr(fn);
+		return str === '[object AsyncFunction]';
+	}
+	if (!getProto) {
+		return false;
+	}
+	var asyncFunc = getAsyncFunc();
+	return asyncFunc && asyncFunc.prototype === getProto(fn);
+};