feat: duplicate project

[kleenkanteen]

What does this PR do?

Adds a cloneSceneGraph() utility function to the core package. It enables cloning a scene so that the host app can duplicate it. Implements #157

How to test

1. Check out the branch and then create a scene with multiple nodes (walls, items, doors, windows)
2. Clone the scene using cloneSceneGraph()
3. Inspect the Scene Graph Explorer to verify:

• All node IDs are properly regenerated with correct prefixes
• Parent-child relationships are preserved (check parentId and children arrays)

Changes

1. Deep clones all nodes
2. Generates new UUIDs for every node
3. Remaps all internal references (parentId, children arrays, etc.)
4. Returns a clean SceneGraph ready to be saved as a new project

Screenshots / recordings

Vid of me testing a copy of this branch (#179) with an addition, which has a "clone scene" button that calls our utility function: https://cap.so/s/56tstwb0zmggmmm

Checklist

• I've tested this locally with bun dev
• My code follows the existing code style (run bun check to verify)
• I've updated relevant documentation (if applicable)
• This PR targets the main branch