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-array-buffer/test/index.js

@@ -0,0 +1,49 @@
+'use strict';
+
+var test = require('tape');
+var inspect = require('object-inspect');
+var forEach = require('for-each');
+var v = require('es-value-fixtures');
+var availableTypedArrays = require('available-typed-arrays')();
+
+var isArrayBuffer = require('..');
+
+test('isArrayBuffer', function (t) {
+	t.equal(typeof isArrayBuffer, 'function', 'is a function');
+
+	/** @type {unknown[]} */
+	var nonABs = [].concat(
+		// @ts-expect-error TS sucks with [].concat
+		v.primitives,
+		v.objects,
+		typeof SharedArrayBuffer === 'function' ? new SharedArrayBuffer(0) : []
+	);
+	forEach(nonABs, function (nonAB) {
+		t.equal(isArrayBuffer(nonAB), false, inspect(nonAB) + ' is not an ArrayBuffer');
+	});
+
+	t.test('actual ArrayBuffer instances', { skip: typeof ArrayBuffer === 'undefined' }, function (st) {
+		var ab = new ArrayBuffer();
+		st.equal(isArrayBuffer(ab), true, inspect(ab) + ' is an ArrayBuffer');
+
+		var ab42 = new ArrayBuffer(42);
+		st.equal(isArrayBuffer(ab42), true, inspect(ab42) + ' is an ArrayBuffer');
+
+		var dv = new DataView(ab42);
+		st.equal(isArrayBuffer(dv), false, inspect(dv) + ' is not an ArrayBuffer');
+
+		st.end();
+	});
+
+	t.test('Typed Arrays', { skip: availableTypedArrays.length === 0 }, function (st) {
+		forEach(availableTypedArrays, function (TypedArray) {
+			var ta = new global[TypedArray](0);
+			st.equal(isArrayBuffer(ta.buffer), true, inspect(ta.buffer) + ', the TA\'s buffer, is an ArrayBuffer');
+			st.equal(isArrayBuffer(ta), false, inspect(ta) + ' is not an ArrayBuffer');
+		});
+
+		st.end();
+	});
+
+	t.end();
+});