Add a "With errors" filter to the DAG listing

[marciok]

Summary

Add a With errors filter to the DAG listing so users can quickly find DAGs with parsing, compilation, or definition errors.

Acceptance criteria

• The DAG listing includes a clearly labeled With errors filter.
• Enabling the filter shows only DAGs that currently have errors.
• Disabling or clearing the filter restores the full DAG list.
• The filtered list stays correct when DAGs are added, removed, or reloaded through LiveView updates.
• Add LiveView tests for enabling and clearing the filter.