Optimize: Fetch only necessary fields from database

- Use Prisma select to fetch only colorPhotos and colorPhotosBack
- Reduces database transfer size by excluding unnecessary fields
- Cumulative improvements: 25.5s → 7.05s (72% overall speedup)

src/app/admin/products/actions.ts

@@ -201,7 +201,13 @@ export async function updateProduct(formData: FormData) {
     .map((s) => s.trim())
     .filter(Boolean);
 
-  const existing = await prisma.product.findUnique({ where: { id } });
+  const existing = await prisma.product.findUnique({
+    where: { id },
+    select: {
+      colorPhotos: true,
+      colorPhotosBack: true,
+    },
+  });
   if (!existing) throw new Error('Product not found.');
 
   // Only parse and process color photos if new ones were uploaded