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/fast-json-stable-stringify/test/to-json.js

@@ -0,0 +1,22 @@
+'use strict';
+
+var test = require('tape');
+var stringify = require('../');
+
+test('toJSON function', function (t) {
+    t.plan(1);
+    var obj = { one: 1, two: 2, toJSON: function() { return { one: 1 }; } };
+    t.equal(stringify(obj), '{"one":1}' );
+});
+
+test('toJSON returns string', function (t) {
+    t.plan(1);
+    var obj = { one: 1, two: 2, toJSON: function() { return 'one'; } };
+    t.equal(stringify(obj), '"one"');
+});
+
+test('toJSON returns array', function (t) {
+    t.plan(1);
+    var obj = { one: 1, two: 2, toJSON: function() { return ['one']; } };
+    t.equal(stringify(obj), '["one"]');
+});