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/@babel/runtime/regenerator/index.js

@@ -0,0 +1,15 @@
+// TODO(Babel 8): Remove this file.
+
+var runtime = require("../helpers/regeneratorRuntime")();
+module.exports = runtime;
+
+// Copied from https://github.com/facebook/regenerator/blob/main/packages/runtime/runtime.js#L736=
+try {
+  regeneratorRuntime = runtime;
+} catch (accidentalStrictMode) {
+  if (typeof globalThis === "object") {
+    globalThis.regeneratorRuntime = runtime;
+  } else {
+    Function("r", "regeneratorRuntime = r")(runtime);
+  }
+}