feat: unify CLI and API with DataService trait

- Add DataService trait with streaming support for save/get operations
- Implement SyncDataService for CLI and AsyncDataService for API
- Add missing API endpoints: DELETE /api/item/{id}, GET /api/item/{id}/info, GET /api/diff
- Add GET /api/plugins/status endpoint
- Preserve stdin/stdout streaming performance via Read trait

src/services/mod.rs

@@ -1,17 +1,23 @@
+pub mod async_data_service;
 pub mod async_item_service;
 pub mod compression_service;
+pub mod data_service;
 pub mod error;
 pub mod filter_service;
 pub mod item_service;
 pub mod meta_service;
 pub mod status_service;
+pub mod sync_data_service;
 pub mod types;
 
+pub use async_data_service::AsyncDataService;
 pub use async_item_service::AsyncItemService;
 pub use compression_service::CompressionService;
+pub use data_service::DataService;
 pub use error::CoreError;
 pub use filter_service::{FilterService, register_filter_plugin};
 pub use item_service::ItemService;
 pub use meta_service::MetaService;
 pub use status_service::StatusService;
+pub use sync_data_service::SyncDataService;
 pub use types::{ItemWithContent, ItemWithMeta};