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-build/tsconfig.json

@@ -0,0 +1,23 @@
+{
+  "extends": "../../tsconfig",
+  "compilerOptions": {
+    "composite": true,
+    "esModuleInterop": true,
+    "module": "CommonJS",
+    "outDir": "./build",
+    "resolveJsonModule": true,
+    "rootDir": "./src",
+    "target": "ES2018",
+    "tsBuildInfoFile": "./tsconfig.tsbuildinfo"
+  },
+  "files": ["src/cdn-details.json"],
+  "include": ["src/**/*.ts", "src/schema/*.json"],
+  "references": [
+    {"path": "../workbox-background-sync/"},
+    {"path": "../workbox-broadcast-update/"},
+    {"path": "../workbox-cacheable-response/"},
+    {"path": "../workbox-core/"},
+    {"path": "../workbox-expiration/"},
+    {"path": "../workbox-google-analytics/"}
+  ]
+}