feat: local backup (#5054)

* feat: local backup

* refactor(backup): make local backup helpers synchronous and clean up redundant checks

- Converted local backup helpers to synchronous functions to remove unused async warnings and align command signatures.
- Updated list/delete/export commands to call the sync feature functions directly without awaits while preserving behavior.
- Simplified destination directory creation to always ensure parent folders exist without redundant checks, satisfying Clippy.

src-tauri/src/lib.rs

@@ -204,6 +204,11 @@ mod app_init {
             cmd::script_validate_notice,
             cmd::validate_script_file,
             // Backup and WebDAV
+            cmd::create_local_backup,
+            cmd::list_local_backup,
+            cmd::delete_local_backup,
+            cmd::restore_local_backup,
+            cmd::export_local_backup,
             cmd::create_webdav_backup,
             cmd::save_webdav_config,
             cmd::list_webdav_backup,