Add Actions header for the studies table action column

[mohiuddinshahrukh]

Summary

Adds a visible header label for the last column in the studies table so the column purpose is clear.

Changes

• Updated designer_v2/lib/features/dashboard/studies_table.dart.
• Set the StudiesTableColumn.action header title to Actions.
• Kept the action column non-sortable (no sorting behavior added).

Scope

• UI-only table header labeling change.
• No data, backend, or sorting logic behavior changes.

Validation

• Verified the studies table now shows Actions as the last column header.
• Verified the Actions column remains non-sortable.

[johannesvedder]

Thanks for the idea. I think if the column only contains an ellipsis menu and is not sortable/filterable, we can leave the header visually empty to reduce noise. We still have a tooltip for the menu to provide explanation, so this keeps the table clean without losing clarity

[mohiuddinshahrukh]

Thanks for the feedback.

The intention behind this was to follow convention: If all columns have headers, then this should also follow the convention, it makes the table look more aligned but I guess this can be taken as food for thought and considered later on aswell to be something included or left out!