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-broadcast-update/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "workbox-broadcast-update",
+  "version": "7.4.0",
+  "license": "MIT",
+  "author": "Google's Web DevRel Team and Google's Aurora Team",
+  "description": "A service worker helper library that uses the Broadcast Channel API to announce when a cached response has updated",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/googlechrome/workbox.git"
+  },
+  "bugs": "https://github.com/googlechrome/workbox/issues",
+  "homepage": "https://github.com/GoogleChrome/workbox",
+  "keywords": [
+    "workbox",
+    "workboxjs",
+    "service worker",
+    "sw",
+    "workbox-plugin"
+  ],
+  "workbox": {
+    "browserNamespace": "workbox.broadcastUpdate",
+    "packageType": "sw"
+  },
+  "main": "index.js",
+  "module": "index.mjs",
+  "types": "index.d.ts",
+  "dependencies": {
+    "workbox-core": "7.4.0"
+  },
+  "gitHead": "fa702feeddd417fcdfa495cd9428fb4a28632e92"
+}