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/index.d.ts

@@ -0,0 +1,12 @@
+import { NavigationRoute, NavigationRouteMatchOptions } from './NavigationRoute.js';
+import { RegExpRoute } from './RegExpRoute.js';
+import { registerRoute } from './registerRoute.js';
+import { Route } from './Route.js';
+import { Router } from './Router.js';
+import { setCatchHandler } from './setCatchHandler.js';
+import { setDefaultHandler } from './setDefaultHandler.js';
+import './_version.js';
+/**
+ * @module workbox-routing
+ */
+export { NavigationRoute, RegExpRoute, registerRoute, Route, Router, setCatchHandler, setDefaultHandler, NavigationRouteMatchOptions, };