Add native sticky header support to DataGrid without requiring virtualization

Currently, HeroUI Pro DataGrid appears to support sticky headers mainly through the virtualized mode, using rowHeight and headingHeight. That works visually, but it forces the table into fixed row heights and virtualization even when the only requirement is keeping the column header visible during vertical scrolling.

It would be useful to have a native prop such as:

<DataGrid stickyHeader />

or:

<DataGrid headerBehavior="sticky" />

This would allow the regular DataGrid to keep dynamic row heights, selection, horizontal scrolling, pagination, and normal table behavior while keeping the header fixed inside the scroll container.