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/electron-to-chromium/package.json

@@ -0,0 +1,44 @@
+{
+  "name": "electron-to-chromium",
+  "version": "1.5.307",
+  "description": "Provides a list of electron-to-chromium version mappings",
+  "main": "index.js",
+  "files": [
+    "versions.js",
+    "full-versions.js",
+    "chromium-versions.js",
+    "full-chromium-versions.js",
+    "versions.json",
+    "full-versions.json",
+    "chromium-versions.json",
+    "full-chromium-versions.json",
+    "LICENSE"
+  ],
+  "scripts": {
+    "build": "node build.mjs",
+    "update": "node automated-update.js",
+    "test": "nyc ava --verbose",
+    "report": "nyc report --reporter=text-lcov > coverage.lcov && codecov"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/kilian/electron-to-chromium.git"
+  },
+  "keywords": [
+    "electron",
+    "chrome",
+    "chromium",
+    "browserslist",
+    "browserlist"
+  ],
+  "author": "Kilian Valkhof",
+  "license": "ISC",
+  "devDependencies": {
+    "ava": "^5.1.1",
+    "codecov": "^3.8.2",
+    "compare-versions": "^6.0.0-rc.1",
+    "node-fetch": "^3.3.0",
+    "nyc": "^15.1.0",
+    "shelljs": "^0.8.5"
+  }
+}