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-routing/setCatchHandler.js

@@ -0,0 +1,23 @@
+/*
+  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 { getOrCreateDefaultRouter } from './utils/getOrCreateDefaultRouter.js';
+import './_version.js';
+/**
+ * If a Route throws an error while handling a request, this `handler`
+ * will be called and given a chance to provide a response.
+ *
+ * @param {workbox-routing~handlerCallback} handler A callback
+ * function that returns a Promise resulting in a Response.
+ *
+ * @memberof workbox-routing
+ */
+function setCatchHandler(handler) {
+    const defaultRouter = getOrCreateDefaultRouter();
+    defaultRouter.setCatchHandler(handler);
+}
+export { setCatchHandler };