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/vite-plugin-pwa/pwa-assets.d.ts

@@ -0,0 +1,40 @@
+/* WARNING: these virtual modules are meant to be used by integrations and not being consumed directly from applications */
+
+declare module 'virtual:pwa-assets/head' {
+  export interface PWAAssetHeadLink {
+    id?: string
+    rel: 'apple-touch-startup-image' | 'apple-touch-icon' | 'icon'
+    href: string
+    media?: string
+    sizes?: string
+    type?: string
+  }
+
+  export interface ColorSchemeMeta {
+    name: string
+    content: string
+  }
+
+  export interface PWAAssetsHead {
+    links: PWAAssetHeadLink[]
+    themeColor?: ColorSchemeMeta
+  }
+
+  export const pwaAssetsHead: PWAAssetsHead
+}
+
+declare module 'virtual:pwa-assets/icons' {
+  import type { AppleSplashScreenLink, FaviconLink, HtmlLink, IconAsset } from '@vite-pwa/assets-generator/api'
+
+  export type PWAAssetIcon<T extends HtmlLink> = Omit<IconAsset<T>, 'buffer'>
+
+  export interface PWAAssetsIcons {
+    favicon: Record<string, PWAAssetIcon<FaviconLink>>
+    transparent: Record<string, PWAAssetIcon<HtmlLink>>
+    maskable: Record<string, PWAAssetIcon<HtmlLink>>
+    apple: Record<string, PWAAssetIcon<HtmlLink>>
+    appleSplashScreen: Record<string, PWAAssetIcon<AppleSplashScreenLink>>
+  }
+
+  export const pwaAssetsIcons: PWAAssetsIcons
+}