P1: AsyncS3Vfs implementation (Phase 3)

- AsyncS3Vfs: spawn_blocking wrapper over S3Vfs
- AsyncS3File: tokio::sync::Mutex for async state
- Add Clone derive to S3Vfs
- All backend methods wrapped with spawn_blocking

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

Tests: 293 passed, 0 failed

markbase-core/src/vfs/s3_fs.rs

@@ -8,6 +8,7 @@ use std::time::{Duration, SystemTime};
 use url::Url;
 
 /// S3-compatible 文件系統後端
+#[derive(Clone)]
 pub struct S3Vfs {
     bucket: Bucket,
     credentials: Credentials,
@@ -417,6 +418,28 @@ impl VfsBackend for S3Vfs {
         let to_key = Self::path_to_key(link);
         self.copy_object(&from_key, &to_key)
     }
+
+    fn copy(&self, from: &Path, to: &Path) -> Result<(), VfsError> {
+        let from_key = Self::path_to_key(from);
+        let to_key = Self::path_to_key(to);
+
+        // Check if source is a directory marker
+        if from.ends_with("/") || from_key.ends_with('/') {
+            // Directory copy: create destination directory marker
+            let action = actions::PutObject::new(&self.bucket, Some(&self.credentials), &to_key);
+            let url = action.sign(Duration::from_secs(3600));
+            ureq::put(url.as_str())
+                .send_bytes(&[])
+                .map_err(|e| VfsError::Io(format!("S3 PutObject failed: {}", e)))?;
+            return Ok(());
+        }
+
+        // Try HeadObject to verify source exists
+        match self.head_object(&from_key) {
+            Ok(_) => self.copy_object(&from_key, &to_key),
+            Err(e) => Err(e),
+        }
+    }
 }
 
 impl VfsFile for S3VfsFile {