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/precache.js

@@ -0,0 +1,33 @@
+/*
+  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';
+/**
+ * Adds items to the precache list, removing any duplicates and
+ * stores the files in the
+ * {@link workbox-core.cacheNames|"precache cache"} when the service
+ * worker installs.
+ *
+ * This method can be called multiple times.
+ *
+ * Please note: This method **will not** serve any of the cached files for you.
+ * It only precaches files. To respond to a network request you call
+ * {@link workbox-precaching.addRoute}.
+ *
+ * If you have a single array of files to precache, you can just call
+ * {@link workbox-precaching.precacheAndRoute}.
+ *
+ * @param {Array<Object|string>} [entries=[]] Array of entries to precache.
+ *
+ * @memberof workbox-precaching
+ */
+function precache(entries) {
+    const precacheController = getOrCreatePrecacheController();
+    precacheController.precache(entries);
+}
+export { precache };