Adds grab-to-pan horizontal scrolling to the Kanban dashboard board
columns with grab/grabbing cursor feedback. Card drag-and-drop, add
buttons, checkboxes, links, and inputs are excluded from panning, the
native horizontal scrollbar remains usable as a fallback, and panning
state is cleared on mouse release or window blur.
Salvaged from PR #59830 by @vampyren (original commit authored under an
unlinked local git identity; rewritten to their GitHub noreply address
to preserve attribution).
cc0aa18fe7