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/lib/homedir.js

@@ -0,0 +1,24 @@
+'use strict';
+
+var os = require('os');
+
+// adapted from https://github.com/sindresorhus/os-homedir/blob/11e089f4754db38bb535e5a8416320c4446e8cfd/index.js
+
+module.exports = os.homedir || function homedir() {
+    var home = process.env.HOME;
+    var user = process.env.LOGNAME || process.env.USER || process.env.LNAME || process.env.USERNAME;
+
+    if (process.platform === 'win32') {
+        return process.env.USERPROFILE || process.env.HOMEDRIVE + process.env.HOMEPATH || home || null;
+    }
+
+    if (process.platform === 'darwin') {
+        return home || (user ? '/Users/' + user : null);
+    }
+
+    if (process.platform === 'linux') {
+        return home || (process.getuid() === 0 ? '/root' : (user ? '/home/' + user : null)); // eslint-disable-line no-extra-parens
+    }
+
+    return home || null;
+};