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/resolve/test/subdirs.js

@@ -0,0 +1,13 @@
+var test = require('tape');
+var resolve = require('../');
+var path = require('path');
+
+test('subdirs', function (t) {
+    t.plan(2);
+
+    var dir = path.join(__dirname, '/subdirs');
+    resolve('a/b/c/x.json', { basedir: dir }, function (err, res) {
+        t.ifError(err);
+        t.equal(res, path.join(dir, 'node_modules/a/b/c/x.json'));
+    });
+});