feat(wallpaper): add apply_wallpaper workflow and rotation worker

Adds a new apply_wallpaper command and its plumbing across
desktop, mobile, and Android. A WorkManager-based rotation
worker handles applying wallpapers in the background. Wallpaper
state now tracks currentId and imageIds for precise control.

- Introduced apply_wallpaper command across desktop, mobile and Android
- Added WorkManager-based rotation worker to apply wallpapers in the
  background
- Extended wallpaper state with currentId and imageIds and updated schemas/permissions

plugins/src/desktop.rs

@@ -22,6 +22,8 @@ impl<R: Runtime> Wallpaper<R> {
             shuffle: true,
             lock_screen_only: true,
             current_index: 0,
+            current_id: Some("demo-0".into()),
+            image_ids: vec!["demo-0".into(), "demo-1".into(), "demo-2".into()],
             image_urls: vec![
                 "/wallpapers/alpine.png".into(),
                 "/wallpapers/waterfall.png".into(),
@@ -100,6 +102,15 @@ impl<R: Runtime> Wallpaper<R> {
     pub fn next_wallpaper(&self) -> crate::Result<WallpaperState> {
         let mut state = Self::demo();
         state.current_index = 1;
+        state.current_id = Some("demo-1".into());
+        Ok(state)
+    }
+    pub fn apply_wallpaper(&self, payload: ApplyWallpaperRequest) -> crate::Result<WallpaperState> {
+        let mut state = Self::demo();
+        if let Some(index) = state.image_ids.iter().position(|id| id == &payload.id) {
+            state.current_index = index;
+            state.current_id = Some(payload.id);
+        }
         Ok(state)
     }
     pub fn get_immich_connection(&self) -> crate::Result<ImmichConnection> {