fix: add isFavorite on Product show response

backend/app/Http/Controllers/ProductController.php

@@ -27,7 +27,10 @@ public function store(CreateProductRequest $request)
 
     public function show(string $slug)
     {
-        $product = Product::where('slug', $slug)->with(['category:id,name,slug', 'images:id,path,product_id'])->firstOrFail();
+        $product = Product::where('slug', $slug)
+            ->with(['category:id,name,slug', 'images:id,path,product_id'])
+            ->withExists('favoritedBy')
+            ->firstOrFail();
 
         return new ProductResource(ProductDTO::fromModel($product));
     }