实现 /api/playlist 快照语义，返回 playlist 和 current_index

- 新增 PlaylistSnapshot 结构体，包含 playlist 和 current_index
- 修改 playlist_route 从 HttpState 获取 player_status.current_index
- 与旧版 hologram_player_rust 行为一致
- cargo check 零 warning

src/plugins/http/routes.rs

@@ -57,6 +57,12 @@ struct BleStatusResponse {
     device_name: String,
 }
 
+#[derive(Serialize)]
+struct PlaylistSnapshot {
+    playlist: Vec<crate::core::config::VideoItem>,
+    current_index: usize,
+}
+
 pub(crate) fn build_routes(
     tx: mpsc::Sender<Envelope>,
     state: Arc<HttpState>,
@@ -212,7 +218,12 @@ fn playlist_route(
         .and(with_state(state))
         .and_then(|state: Arc<HttpState>| async move {
             let config = state.config();
-            Ok::<_, Infallible>(json_response(StatusCode::OK, &config.playlist))
+            let player_status = state.player_status();
+            let snapshot = PlaylistSnapshot {
+                playlist: config.playlist.clone(),
+                current_index: player_status.current_index,
+            };
+            Ok::<_, Infallible>(json_response(StatusCode::OK, &snapshot))
         })
 }