This commit replaces the placeholder implementation of the SkillTreeView class with a complete, functional version.
Features:
- Initializes the skill tree from the SkillTreeViewModel during `initState`.
- Dynamically creates Node and Edge objects for GraphView based on ViewModel data.
- Utilizes the TreeNodeView to render individual nodes.
- Integrates node selection functionality from the ViewModel.
- Adds InteractiveViewer for zoom and pan capabilities.
The new SkillTreeView is designed to work closely with SkillTreeViewModel to manage and display the skill tree.
