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/@vitest/snapshot/README.md

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+# @vitest/snapshot
+
+Lightweight implementation of Jest's snapshots.
+
+## Usage
+
+```js
+import { SnapshotClient } from '@vitest/snapshot'
+import { NodeSnapshotEnvironment } from '@vitest/snapshot/environment'
+import { SnapshotManager } from '@vitest/snapshot/manager'
+
+const client = new SnapshotClient({
+  // you need to provide your own equality check implementation if you use it
+  // this function is called when `.toMatchSnapshot({ property: 1 })` is called
+  isEqual: (received, expected) =>
+    equals(received, expected, [iterableEquality, subsetEquality]),
+})
+
+// class that implements snapshot saving and reading
+// by default uses fs module, but you can provide your own implementation depending on the environment
+const environment = new NodeSnapshotEnvironment()
+
+// you need to implement this yourselves,
+// this depends on your runner
+function getCurrentFilepath() {
+  return '/file.spec.js'
+}
+function getCurrentTestName() {
+  return 'test1'
+}
+
+// example for inline snapshots, nothing is required to support regular snapshots,
+// just call `assert` with `isInline: false`
+function wrapper(received) {
+  function __INLINE_SNAPSHOT__(inlineSnapshot, message) {
+    client.assert({
+      received,
+      message,
+      isInline: true,
+      inlineSnapshot,
+      filepath: getCurrentFilepath(),
+      name: getCurrentTestName(),
+    })
+  }
+  return {
+    // the name is hard-coded, it should be inside another function, so Vitest can find the actual test file where it was called (parses call stack trace + 2)
+    // you can override this behaviour in SnapshotState's `_inferInlineSnapshotStack` method by providing your own SnapshotState to SnapshotClient constructor
+    toMatchInlineSnapshot: (...args) => __INLINE_SNAPSHOT__(...args),
+  }
+}
+
+const options = {
+  updateSnapshot: 'new',
+  snapshotEnvironment: environment,
+}
+
+await client.startCurrentRun(
+  getCurrentFilepath(),
+  getCurrentTestName(),
+  options
+)
+
+// this will save snapshot to a file which is returned by "snapshotEnvironment.resolvePath"
+client.assert({
+  received: 'some text',
+  isInline: false,
+})
+
+// uses "pretty-format", so it requires quotes
+// also naming is hard-coded when parsing test files
+wrapper('text 1').toMatchInlineSnapshot()
+wrapper('text 2').toMatchInlineSnapshot('"text 2"')
+
+const result = await client.finishCurrentRun() // this saves files and returns SnapshotResult
+
+// you can use manager to manage several clients
+const manager = new SnapshotManager(options)
+manager.add(result)
+
+// do something
+// and then read the summary
+
+console.log(manager.summary)
+```