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/workbox-precaching/matchPrecache.js

@@ -0,0 +1,29 @@
+/*
+  Copyright 2019 Google LLC
+
+  Use of this source code is governed by an MIT-style
+  license that can be found in the LICENSE file or at
+  https://opensource.org/licenses/MIT.
+*/
+import { getOrCreatePrecacheController } from './utils/getOrCreatePrecacheController.js';
+import './_version.js';
+/**
+ * Helper function that calls
+ * {@link PrecacheController#matchPrecache} on the default
+ * {@link PrecacheController} instance.
+ *
+ * If you are creating your own {@link PrecacheController}, then call
+ * {@link PrecacheController#matchPrecache} on that instance,
+ * instead of using this function.
+ *
+ * @param {string|Request} request The key (without revisioning parameters)
+ * to look up in the precache.
+ * @return {Promise<Response|undefined>}
+ *
+ * @memberof workbox-precaching
+ */
+function matchPrecache(request) {
+    const precacheController = getOrCreatePrecacheController();
+    return precacheController.matchPrecache(request);
+}
+export { matchPrecache };