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-node/dist/constants.mjs

@@ -0,0 +1,38 @@
+const KNOWN_ASSET_TYPES = [
+  // images
+  "apng",
+  "bmp",
+  "png",
+  "jpe?g",
+  "jfif",
+  "pjpeg",
+  "pjp",
+  "gif",
+  "svg",
+  "ico",
+  "webp",
+  "avif",
+  // media
+  "mp4",
+  "webm",
+  "ogg",
+  "mp3",
+  "wav",
+  "flac",
+  "aac",
+  // fonts
+  "woff2?",
+  "eot",
+  "ttf",
+  "otf",
+  // other
+  "webmanifest",
+  "pdf",
+  "txt"
+];
+const KNOWN_ASSET_RE = new RegExp(
+  `\\.(${KNOWN_ASSET_TYPES.join("|")})$`
+);
+const CSS_LANGS_RE = /\.(css|less|sass|scss|styl|stylus|pcss|postcss|sss)(?:$|\?)/;
+
+export { CSS_LANGS_RE, KNOWN_ASSET_RE, KNOWN_ASSET_TYPES };