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-recipes/warmStrategyCache.js

@@ -0,0 +1,18 @@
+import './_version.js';
+/**
+ * @memberof workbox-recipes
+ 
+ * @param {Object} options
+ * @param {string[]} options.urls Paths to warm the strategy's cache with
+ * @param {Strategy} options.strategy Strategy to use
+ */
+function warmStrategyCache(options) {
+    self.addEventListener('install', (event) => {
+        const done = options.urls.map((path) => options.strategy.handleAll({
+            event,
+            request: new Request(path),
+        })[1]);
+        event.waitUntil(Promise.all(done));
+    });
+}
+export { warmStrategyCache };