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/utils/calculateEffectiveBoundaries.d.ts

@@ -0,0 +1,16 @@
+import '../_version.js';
+/**
+ * @param {Blob} blob A source blob.
+ * @param {number} [start] The offset to use as the start of the
+ * slice.
+ * @param {number} [end] The offset to use as the end of the slice.
+ * @return {Object} An object with `start` and `end` properties, reflecting
+ * the effective boundaries to use given the size of the blob.
+ *
+ * @private
+ */
+declare function calculateEffectiveBoundaries(blob: Blob, start?: number, end?: number): {
+    start: number;
+    end: number;
+};
+export { calculateEffectiveBoundaries };