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-range-requests/RangeRequestsPlugin.d.ts

@@ -0,0 +1,26 @@
+import { WorkboxPlugin } from 'workbox-core/types.js';
+import './_version.js';
+/**
+ * The range request plugin makes it easy for a request with a 'Range' header to
+ * be fulfilled by a cached response.
+ *
+ * It does this by intercepting the `cachedResponseWillBeUsed` plugin callback
+ * and returning the appropriate subset of the cached response body.
+ *
+ * @memberof workbox-range-requests
+ */
+declare class RangeRequestsPlugin implements WorkboxPlugin {
+    /**
+     * @param {Object} options
+     * @param {Request} options.request The original request, which may or may not
+     * contain a Range: header.
+     * @param {Response} options.cachedResponse The complete cached response.
+     * @return {Promise<Response>} If request contains a 'Range' header, then a
+     * new response with status 206 whose body is a subset of `cachedResponse` is
+     * returned. Otherwise, `cachedResponse` is returned as-is.
+     *
+     * @private
+     */
+    cachedResponseWillBeUsed: WorkboxPlugin['cachedResponseWillBeUsed'];
+}
+export { RangeRequestsPlugin };