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/unicode-match-property-ecmascript/package.json

@@ -0,0 +1,39 @@
+{
+  "name": "unicode-match-property-ecmascript",
+  "version": "2.0.0",
+  "description": "Match a Unicode property or property alias to its canonical property name per the algorithm used for RegExp Unicode property escapes in ECMAScript.",
+  "homepage": "https://github.com/mathiasbynens/unicode-match-property-ecmascript",
+  "main": "index.js",
+  "engines": {
+    "node": ">=4"
+  },
+  "files": [
+    "LICENSE-MIT.txt",
+    "index.js"
+  ],
+  "keywords": [
+    "unicode",
+    "unicode properties",
+    "unicode property aliases"
+  ],
+  "license": "MIT",
+  "author": {
+    "name": "Mathias Bynens",
+    "url": "https://mathiasbynens.be/"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/mathiasbynens/unicode-match-property-ecmascript.git"
+  },
+  "bugs": "https://github.com/mathiasbynens/unicode-match-property-ecmascript/issues",
+  "dependencies": {
+    "unicode-canonical-property-names-ecmascript": "^2.0.0",
+    "unicode-property-aliases-ecmascript": "^2.0.0"
+  },
+  "devDependencies": {
+    "ava": "*"
+  },
+  "scripts": {
+    "test": "ava ./tests/*"
+  }
+}