[Improvement] Gravitino UI / Playground Iceberg catalog missing content

### What would you like to be improved?

Iceberg catalog contains no content:

### How should we improve?

Add content to the Iceberg catalog.

The issue points to the Gravitino UI/Playground Iceberg catalog and includes a screenshot, but names no files, tests, or expected content. Start by locating the catalog view and tracing how its content is populated; clarify with maintainers what content should appear, then verify the Iceberg catalog displays it.

Written by the indexing model from the issue text.