Clear localStorage draft when design submitted for approval

Also remove the designDraft from localStorage when submission succeeds,
so the cleared state doesn't get reloaded when the user creates another design.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/components/DesignCanvas.tsx

@@ -967,6 +967,7 @@ export default function DesignCanvas({ product, isAdminEditing = false }: { prod
           setElementsBack([]);
           // Save to localStorage so status persists on page reload
           if (typeof window !== 'undefined') {
+            localStorage.removeItem(`designDraft_${product.id}`);
             localStorage.setItem(`designApproval_${product.id}`, JSON.stringify({
               id: design.id,
               status: 'PENDING',