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/vite/dist/client/env.mjs

@@ -0,0 +1,24 @@
+const context = (() => {
+  if (typeof globalThis !== "undefined") {
+    return globalThis;
+  } else if (typeof self !== "undefined") {
+    return self;
+  } else if (typeof window !== "undefined") {
+    return window;
+  } else {
+    return Function("return this")();
+  }
+})();
+const defines = __DEFINES__;
+Object.keys(defines).forEach((key) => {
+  const segments = key.split(".");
+  let target = context;
+  for (let i = 0; i < segments.length; i++) {
+    const segment = segments[i];
+    if (i === segments.length - 1) {
+      target[segment] = defines[key];
+    } else {
+      target = target[segment] || (target[segment] = {});
+    }
+  }
+});