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/cross-spawn/lib/util/readShebang.js

@@ -0,0 +1,23 @@
+'use strict';
+
+const fs = require('fs');
+const shebangCommand = require('shebang-command');
+
+function readShebang(command) {
+    // Read the first 150 bytes from the file
+    const size = 150;
+    const buffer = Buffer.alloc(size);
+
+    let fd;
+
+    try {
+        fd = fs.openSync(command, 'r');
+        fs.readSync(fd, buffer, 0, size, 0);
+        fs.closeSync(fd);
+    } catch (e) { /* Empty */ }
+
+    // Attempt to extract shebang (null is returned if not a shebang)
+    return shebangCommand(buffer.toString());
+}
+
+module.exports = readShebang;