Fix: Include imageUrl/imageUrlBack in database select query

- Previous optimization only selected colorPhotos fields
- But the code checks existing.imageUrl to decide if print area should update
- imageUrl/imageUrlBack were undefined, breaking the print area update logic
- Now properly includes these fields in the select so the check works

src/app/admin/products/actions.ts

@@ -206,6 +206,8 @@ export async function updateProduct(formData: FormData) {
     select: {
       colorPhotos: true,
       colorPhotosBack: true,
+      imageUrl: true,
+      imageUrlBack: true,
     },
   });
   if (!existing) throw new Error('Product not found.');