Display Post-Run Data Statistics

[Edwardvaneechoud]

Description:
Provide users with immediate insights into the data produced by each node.

Requirements:

• Backend Task: After a node successfully executes, the backend should calculate basic statistics on the resulting Polars DataFrame (e.g., df.shape for row/column count and df.estimated_size() for memory usage).
• Frontend Task: These statistics should be sent to the frontend and displayed in a dedicated panel or directly on the node itself, giving the user instant feedback like "10,000 rows, 15 columns, 2.3 MB."