v1.1.4: DataTable: stack below 920px, per-column classes, wrapping toolbar

- .table-stacked now turns rows into cards below 920px (was 576px): a table
  with a link, a date and actions is already cramped on a laptop beside a
  sidebar. The toolbar follows the same query (.data-table-toolbar /
  .data-table-actions): search and buttons each take a full row, centred.
- TableColumn takes an optional cssClass for the header cell. Not `$class`:
  parameter names reach the transpiled JS verbatim and `class` is reserved,
  which fails the whole bundle.
- .table-col-wide-only hides a column only between 920 and 1199px, where the
  table is still a grid but narrow; stacked cards show the field again.
- The toolbar's actions are a wrapping flex row with a gap, so buttons that run
  out of room wrap cleanly. Slot buttons need no margins of their own.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>