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/addRoute.d.ts

@@ -0,0 +1,19 @@
+import { PrecacheRouteOptions } from './_types.js';
+import './_version.js';
+/**
+ * Add a `fetch` listener to the service worker that will
+ * respond to
+ * [network requests]{@link https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API/Using_Service_Workers#Custom_responses_to_requests}
+ * with precached assets.
+ *
+ * Requests for assets that aren't precached, the `FetchEvent` will not be
+ * responded to, allowing the event to fall through to other `fetch` event
+ * listeners.
+ *
+ * @param {Object} [options] See the {@link workbox-precaching.PrecacheRoute}
+ * options.
+ *
+ * @memberof workbox-precaching
+ */
+declare function addRoute(options?: PrecacheRouteOptions): void;
+export { addRoute };