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/leaflet.offline/examples/map-layers-and-control/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "map-layers-and-control",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc && vite build",
+    "preview": "vite preview",
+    "format": "prettier -w ."
+  },
+  "devDependencies": {
+    "prettier": "^3.3.3",
+    "typescript": "~5.6.2",
+    "vite": "^5.4.19"
+  },
+  "dependencies": {
+    "@fortawesome/fontawesome-free": "^6.6.0",
+    "@fortawesome/free-solid-svg-icons": "^6.6.0",
+    "debounce": "^2.2.0",
+    "idb": "^8.0.0",
+    "leaflet": "^1.9.4",
+    "leaflet.offline": "^3.1.0"
+  }
+}