P1: AsyncLocalFs implementation (Phase 2)

- AsyncLocalFile: tokio::fs::File wrapper
- AsyncLocalFs: AsyncVfsBackend impl using tokio::fs
- Key methods: read_dir, open_file, stat, create_dir, remove_file, rename
- 4 async tests passing

Phase 2 complete: AsyncLocalFs working
Phase 3 pending: AsyncS3Vfs
Phase 4 pending: AsyncSmbVfs
Phase 5 pending: WebDAV integration

Tests: 293 passed, 0 failed

markbase-core/src/vfs/mod.rs

@@ -8,6 +8,8 @@ pub mod smb_fs;
 #[cfg(feature = "smb-server")]
 pub mod smb_server_backend;
 pub mod util;
+#[cfg(feature = "async-vfs")]
+pub mod async_fs;
 
 use std::path::{Path, PathBuf};
 use std::time::SystemTime;
@@ -567,7 +569,7 @@ pub trait AsyncVfsFile: Send + Sync {
     fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<usize, VfsError>> + Send + 'a>>;
     fn write<'a>(&'a mut self, buf: &'a [u8]) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<usize, VfsError>> + Send + 'a>>;
     fn seek<'a>(&'a mut self, pos: std::io::SeekFrom) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<u64, VfsError>> + Send + 'a>>;
-    fn flush(&mut self) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<(), VfsError>> + Send>>;
+    fn flush<'a>(&'a mut self) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<(), VfsError>> + Send + 'a>>;
 }
 
 /// Async VFS 后端 trait（用于异步文件系统操作）