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/@vitest/snapshot/dist/environment.js

@@ -0,0 +1,43 @@
+import { promises, existsSync } from 'node:fs';
+import { isAbsolute, resolve, dirname, join, basename } from 'pathe';
+
+class NodeSnapshotEnvironment {
+  constructor(options = {}) {
+    this.options = options;
+  }
+  getVersion() {
+    return "1";
+  }
+  getHeader() {
+    return `// Snapshot v${this.getVersion()}`;
+  }
+  async resolveRawPath(testPath, rawPath) {
+    return isAbsolute(rawPath) ? rawPath : resolve(dirname(testPath), rawPath);
+  }
+  async resolvePath(filepath) {
+    return join(
+      join(dirname(filepath), this.options.snapshotsDirName ?? "__snapshots__"),
+      `${basename(filepath)}.snap`
+    );
+  }
+  async prepareDirectory(dirPath) {
+    await promises.mkdir(dirPath, { recursive: true });
+  }
+  async saveSnapshotFile(filepath, snapshot) {
+    await promises.mkdir(dirname(filepath), { recursive: true });
+    await promises.writeFile(filepath, snapshot, "utf-8");
+  }
+  async readSnapshotFile(filepath) {
+    if (!existsSync(filepath)) {
+      return null;
+    }
+    return promises.readFile(filepath, "utf-8");
+  }
+  async removeSnapshotFile(filepath) {
+    if (existsSync(filepath)) {
+      await promises.unlink(filepath);
+    }
+  }
+}
+
+export { NodeSnapshotEnvironment };