Introduce a new SupplierGroup component and group collections by supplier. Add supplier color palette, per-supplier expand/collapse state, compact/detailed view modes, and controls to toggle/expand/collapse groups. Pass supplierColor and compact props to CollectionItemCard to adjust visuals, use useMemo for grouping, and auto-expand suppliers on initial load. Minor UI tweaks: adjust skeleton count/spacing, update stats/controls bar, improve toast styling, and remove some console logs.
