🐛 fix: show VirtualizedTable bottom borders when pagination bar is hidden

[futjesus]

Problem

When VirtualizedTable has pagination enabled (showPagination or any of its variants) but totalItems <= DEFAULT_PAGE_SIZE (10), the Pagination footer returns null — yet WrapperBody and Body still style the table as if the footer were going to draw the bottom edge. The result is square bottom corners and a missing bottom border (especially visible in dark mode).

Fix

The mismatch existed because three components decided the bottom edge from showPagination alone, while only Pagination also considered totalItems:

• Added a shared isPaginationBarVisible(totalItems) predicate in VirtualizedTable/utils as the single source of truth for whether the pagination bar actually renders.
• Pagination now uses the predicate for its early return (same behavior as before).
• WrapperBody also applies rounded-lg when the bar is hidden due to few items.
• Body gates rounded-bl-lg / rounded-br-lg, the dark-mode last-row bottom border, and ExpandableRow's isLastRow on the bar actually being visible, not just on showPagination.
• Secondary fix: the useMemo deriving showPagination in VirtualizedTable.tsx had empty deps, so it never recomputed when pagination props changed — proper deps added.

Testing

• New VirtualizedTable.test.tsx covering: no pagination, pagination enabled with few items (bar hidden → borders closed by the table), and pagination visible (bar closes the borders), plus jest-axe.
• New PaginationWithFewItems story in Light and Dark to verify visually.
• npm run test (455 passed), npm run check:types, npm run lint all green.