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/utils/PrecacheCacheKeyPlugin.js

@@ -0,0 +1,30 @@
+/*
+  Copyright 2020 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 '../_version.js';
+/**
+ * A plugin, designed to be used with PrecacheController, to translate URLs into
+ * the corresponding cache key, based on the current revision info.
+ *
+ * @private
+ */
+class PrecacheCacheKeyPlugin {
+    constructor({ precacheController }) {
+        this.cacheKeyWillBeUsed = async ({ request, params, }) => {
+            // Params is type any, can't change right now.
+            /* eslint-disable */
+            const cacheKey = (params === null || params === void 0 ? void 0 : params.cacheKey) ||
+                this._precacheController.getCacheKeyForURL(request.url);
+            /* eslint-enable */
+            return cacheKey
+                ? new Request(cacheKey, { headers: request.headers })
+                : request;
+        };
+        this._precacheController = precacheController;
+    }
+}
+export { PrecacheCacheKeyPlugin };