Replace masonry grid with an absolute-positioned 12-col canvas: drag to
move, corner to resize, per-card free/overlap toggle (Alt = no-snap).
Geometry persisted (migration 027: dashboard_layout.geom + extras).
Two new addable decorative cards: blank spacer + animated blackflame
(canvas particle flame). Old layout auto-migrates by flow-placement.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
