Lets management post internal status updates that don't appear in the
board portal. Adds status_updates.hidden_from_board and re-creates the
association-scoped RLS SELECT policy so board members can't read hidden
rows (staff still see all). Dialog gains a "Hide from board" toggle, the
board view filters hidden updates, and management cards show a badge.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
