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/sourcemap-codec/package.json

@@ -0,0 +1,53 @@
+{
+  "name": "sourcemap-codec",
+  "version": "1.4.8",
+  "description": "Encode/decode sourcemap mappings",
+  "main": "dist/sourcemap-codec.umd.js",
+  "module": "dist/sourcemap-codec.es.js",
+  "types": "dist/types/sourcemap-codec.d.ts",
+  "scripts": {
+    "test": "mocha",
+    "build": "rm -rf dist && rollup -c && tsc",
+    "pretest": "npm run build",
+    "prepublish": "npm test",
+    "lint": "eslint src",
+    "pretest-coverage": "npm run build",
+    "test-coverage": "rm -rf coverage/* && istanbul cover --report json node_modules/.bin/_mocha -- -u exports -R spec test/test.js",
+    "posttest-coverage": "remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped.json -b dist && remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped.lcov -t lcovonly -b dist && remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped -t html -b dist",
+    "ci": "npm run test-coverage && codecov < coverage/coverage-remapped.lcov"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/Rich-Harris/sourcemap-codec"
+  },
+  "keywords": [
+    "sourcemap",
+    "vlq"
+  ],
+  "author": "Rich Harris",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/Rich-Harris/sourcemap-codec/issues"
+  },
+  "homepage": "https://github.com/Rich-Harris/sourcemap-codec",
+  "dependencies": {},
+  "devDependencies": {
+    "codecov.io": "^0.1.6",
+    "console-group": "^0.3.3",
+    "eslint": "^6.0.1",
+    "eslint-plugin-import": "^2.18.0",
+    "istanbul": "^0.4.5",
+    "mocha": "^6.1.4",
+    "remap-istanbul": "^0.13.0",
+    "rollup": "^1.16.4",
+    "rollup-plugin-node-resolve": "^5.2.0",
+    "rollup-plugin-typescript": "^1.0.1",
+    "typescript": "^3.5.2"
+  },
+  "files": [
+    "dist/*.js",
+    "dist/*.js.map",
+    "dist/**/*.d.ts",
+    "README.md"
+  ]
+}