Fix SSH FSETSTAT and simplify SCP execution

- Add SSH_FXP_FSETSTAT and SSH_FXP_SETSTAT handlers (return OK)
- Simplify SCP to use system scp command instead of custom handler
- SCP upload/download now working via SFTP protocol
- Add bcrypt debug logging for authentication troubleshooting

markbase-core/src/ssh_server/auth.rs

@@ -119,7 +119,9 @@ impl AuthHandler {
         
         // 使用bcrypt验证密码
         let stored_hash = password_hash.unwrap();
+        info!("Attempting bcrypt verify: password='{}', hash='{}'", password, stored_hash);
         let valid = verify(&password, &stored_hash)?;
+        info!("bcrypt verify result: {}", valid);
         
         if valid {
             info!("Password auth successful for user: {}", user);