Add dependency graph visualizer and editor scaffold

[VEZY]

Summary

• Add a Julia dependency graph view IR with JSON and standalone HTML export.
• Expose model nodes, ports, edge metadata, cycle diagnostics, and a first PreviousTimeStep edit.
• Scaffold a React Flow + ELK frontend for the interactive graph viewer/editor.
• Cover the new graph view and edit path with unit tests.

Testing

• Added and ran unit tests for the dependency graph view, multiscale edges, HTML export, and the first edit-back operation.
• Ran the full Julia test suite successfully.
• Built and typechecked the frontend successfully with Vite and TypeScript.