Add bulk selection checkboxes and action bars to the articles and leads admin pages, replicating the existing supplier bulk pattern. Articles: publish, unpublish, toggle noindex, rebuild, delete (with confirmation dialog). Leads: set status, set heat. Both re-render the results partial after action via HTMX, preserving current filters. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>