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/browserslist/browser.js

@@ -0,0 +1,54 @@
+var BrowserslistError = require('./error')
+
+function noop() {}
+
+module.exports = {
+  loadQueries: function loadQueries() {
+    throw new BrowserslistError(
+      'Sharable configs are not supported in client-side build of Browserslist'
+    )
+  },
+
+  getStat: function getStat(opts) {
+    return opts.stats
+  },
+
+  loadConfig: function loadConfig(opts) {
+    if (opts.config) {
+      throw new BrowserslistError(
+        'Browserslist config are not supported in client-side build'
+      )
+    }
+  },
+
+  loadCountry: function loadCountry() {
+    throw new BrowserslistError(
+      'Country statistics are not supported ' +
+        'in client-side build of Browserslist'
+    )
+  },
+
+  loadFeature: function loadFeature() {
+    throw new BrowserslistError(
+      'Supports queries are not available in client-side build of Browserslist'
+    )
+  },
+
+  currentNode: function currentNode(resolve, context) {
+    return resolve(['maintained node versions'], context)[0]
+  },
+
+  parseConfig: noop,
+
+  readConfig: noop,
+
+  findConfig: noop,
+
+  findConfigFile: noop,
+
+  clearCaches: noop,
+
+  oldDataWarning: noop,
+
+  env: {}
+}