feat(admin): design system audit fixes

- Add CSS design tokens for consistency (--admin-danger-hover, --admin-accent-dot, shadow-md warm tone)
- Replace unicode icons with inline SVG (⋮, ✕, ▼, ▶)
- Consolidate duplicate PageHeader/AdminPageHeader components
- Standardize border-radius (rounded-xl → rounded-lg for ViewModeTabs)
- Remove hardcoded brand UUID in products page
- Replace hardcoded bg-red-600 with CSS variables in delete buttons
- Add AdminButton, AdminFilterTabs, AdminSearchInput, PageHeader design system components
- Fix GlassModal and AdminModal close button styling
- Remove duplicate 'New Lot' button on Route Trace dashboard

src/components/admin/design-system/AdminActionMenu.tsx

@@ -16,7 +16,7 @@ type AdminActionMenuProps = {
   className?: string;
 };
 
-export default function AdminActionMenu({ actions, triggerLabel = "⋮", className = "" }: AdminActionMenuProps) {
+export default function AdminActionMenu({ actions, triggerLabel, className = "" }: AdminActionMenuProps) {
   const [open, setOpen] = useState(false);
   const menuRef = useRef<HTMLDivElement>(null);
 
@@ -41,7 +41,9 @@ export default function AdminActionMenu({ actions, triggerLabel = "⋮", classNa
         onClick={() => setOpen(!open)}
         className="rounded-lg px-2 py-1.5 text-xs text-[var(--admin-text-muted)] hover:text-[var(--admin-text-secondary)] hover:bg-[var(--admin-bg-subtle)] transition-colors"
       >
-        {triggerLabel}
+        <svg className="h-4 w-4" fill="currentColor" viewBox="0 0 20 20">
+          <circle cx="10" cy="4" r="1.5"/><circle cx="10" cy="10" r="1.5"/><circle cx="10" cy="16" r="1.5"/>
+        </svg>
       </button>
 
       {open && (