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/index.js

@@ -0,0 +1,39 @@
+'use strict';
+
+const cp = require('child_process');
+const parse = require('./lib/parse');
+const enoent = require('./lib/enoent');
+
+function spawn(command, args, options) {
+    // Parse the arguments
+    const parsed = parse(command, args, options);
+
+    // Spawn the child process
+    const spawned = cp.spawn(parsed.command, parsed.args, parsed.options);
+
+    // Hook into child process "exit" event to emit an error if the command
+    // does not exists, see: https://github.com/IndigoUnited/node-cross-spawn/issues/16
+    enoent.hookChildProcess(spawned, parsed);
+
+    return spawned;
+}
+
+function spawnSync(command, args, options) {
+    // Parse the arguments
+    const parsed = parse(command, args, options);
+
+    // Spawn the child process
+    const result = cp.spawnSync(parsed.command, parsed.args, parsed.options);
+
+    // Analyze if the command does not exist, see: https://github.com/IndigoUnited/node-cross-spawn/issues/16
+    result.error = result.error || enoent.verifyENOENTSync(result.status, parsed);
+
+    return result;
+}
+
+module.exports = spawn;
+module.exports.spawn = spawn;
+module.exports.sync = spawnSync;
+
+module.exports._parse = parse;
+module.exports._enoent = enoent;