ADD - separate Home and Lock wallpapers

Store independent Home Screen and Lock Screen wallpaper selections, preserve legacy preferences, and route gallery or camera picks to the selected destination. Add the Settings segmented selector and contract coverage.

frontend/src/components/PhoneLockScreen.contract.test.ts

@@ -6,8 +6,18 @@ const styles = readFileSync(
   new URL('../assets/main.css', import.meta.url),
   'utf8',
 )
+const source = readFileSync(
+  new URL('./PhoneLockScreen.vue', import.meta.url),
+  'utf8',
+)
 
 describe('PhoneLockScreen notification theme contract', () => {
+  it('uses the dedicated Lock Screen wallpaper preference', () => {
+    expect(source).toContain('settings.lockWallpaperImageUrl')
+    expect(source).toContain('settings.lockWallpaper')
+    expect(source).not.toContain('settings.wallpaperImageUrl')
+  })
+
   it('uses explicit light and dark notification material tokens', () => {
     expect(styles).toMatch(
       /\.lock-screen\s*\{[^}]*--lock-notification-background:\s*rgb\(38 36 40 \/ 76%\)[^}]*--lock-notification-color:\s*#fff/s,

frontend/src/components/PhoneLockScreen.vue

@@ -74,10 +74,10 @@ const time = computed(() =>
     .trim(),
 )
 const dragStyle = computed<Record<string, string>>(() => {
-  const imageUrl = preferences.value.settings.wallpaperImageUrl
+  const imageUrl = preferences.value.settings.lockWallpaperImageUrl
   return {
     '--lock-drag': `${dragOffset.value}px`,
-    ...(preferences.value.settings.wallpaper === 'custom' && imageUrl
+    ...(preferences.value.settings.lockWallpaper === 'custom' && imageUrl
       ? { '--phone-wallpaper-image': `url(${JSON.stringify(imageUrl)})` }
       : {}),
   }
@@ -289,7 +289,7 @@ onBeforeUnmount(() => {
   <section
     class="lock-screen"
     :class="[
-      `wallpaper--${preferences.settings.wallpaper}`,
+      `wallpaper--${preferences.settings.lockWallpaper}`,
       {
         'lock-screen--dragging': dragging,
         'lock-screen--preview': preview,

frontend/src/components/PhoneSetupAssistant.vue

@@ -115,7 +115,7 @@ function choosePerformance(mode: GraphicsMode): void {
 }
 
 function chooseWallpaper(wallpaper: Exclude<WallpaperId, 'custom'>): void {
-  phone.setWallpaper(wallpaper)
+  phone.setWallpaper(wallpaper, null, 'both')
 }
 
 function toggleApp(appId: BuiltinPhoneAppId): void {