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/safe-push-apply/test/index.js

@@ -0,0 +1,30 @@
+'use strict';
+
+var test = require('tape');
+
+var safePushApply = require('../');
+
+test('safe-push-apply', function (t) {
+	t.equal(typeof safePushApply, 'function', 'is a function');
+	t.equal(safePushApply.length, 2, 'has a length of 2');
+
+	t['throws'](
+		// @ts-expect-error
+		function () { safePushApply({}, []); },
+		TypeError,
+		'throws if target is not an array'
+	);
+
+	var a = [1, 2];
+	var b = [3, 4];
+	safePushApply(a, b);
+	t.deepEqual(a, [1, 2, 3, 4], 'b is pushed into a');
+	t.deepEqual(b, [3, 4], 'b is not modified');
+
+	var c = '567';
+	// @ts-expect-error TS ArrayLike doesn't accept strings for some reason
+	safePushApply(a, c);
+	t.deepEqual(a, [1, 2, 3, 4, '5', '6', '7'], 'works with arraylike source');
+
+	t.end();
+});