Implement Advanced Undo/Redo with Visual History Timeline

Problem

The current undo/redo system is basic and doesn't provide users with a clear view of their editing history. Users can't see what changes will be undone/redone or jump to specific points in history.

Solution

Implement a visual timeline that shows:

• Thumbnail previews of canvas states
• Timestamps of changes
• Ability to jump to any point in history
• Branching history for complex editing workflows

Acceptance Criteria

• Visual timeline widget in the UI
• Thumbnail generation for canvas states
• Jump-to functionality
• History branching support
• Performance optimization for large histories

Technical Details

• Use RepaintBoundary for efficient thumbnail generation
• Implement history as a tree structure instead of linear list
• Add state diffing to avoid storing full states