DataGrid footer support

The Pro DataGrid renders a self-contained <Table> internally (only a Table.ScrollContainer as its child) and exposes no way to use the OSS Table.Footer slot. Today users must render pagination/summary as a separate sibling <div> below the grid (as the team-members demo does) and manually re-apply .table__footer styling to match. There's no footer/renderFooter prop and no children pass-through.