[Feat]: add drag-and-drop support for task reordering

[EhsanKey]

Is there an existing issue that is already proposing this?

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🪄 describe your feature or idea

This feature aims to allow users to reorder tasks via drag-and-drop in the UI.
To support this functionality, the following is required:

• add a position field to the POST /todos/sync endpoint to persist the updated task order
• Include the position field in the response of the GET /todos endpoint to maintain the correct order on the client side