- Updated the TaskCard component to improve the visibility and animation of subtasks, adding a smooth transition effect for better user experience.
- Adjusted the rendering logic to conditionally display the subtasks container based on the task's state, enhancing the overall UI interaction.

…k index management

- Updated drag-and-drop event handlers in EnhancedKanbanBoard to support null task indices, enhancing flexibility during task interactions.
- Adjusted KanbanGroup component to reflect changes in task index handling, ensuring consistent behavior when dragging tasks over empty drop zones.
- Enhanced the visual structure of the KanbanGroup to improve user experience during task creation and management.

…drop

- Implemented a check for task dependencies when moving tasks between groups in the EnhancedKanbanBoard component.
- Integrated alert notifications to inform users if a task cannot be moved due to incomplete dependencies, enhancing user experience and task management integrity.