feat: refactor cart and purchase handling to support polymorphic buyable types and improve code readability

app/Domains/Cart/Resources/CartResource.php

@@ -2,11 +2,12 @@
 
 namespace App\Domains\Cart\Resources;
 
+use App\Domains\Cart\Models\Cart;
 use Illuminate\Http\Request;
 use Illuminate\Http\Resources\Json\JsonResource;
 
 /**
- * @mixin \App\Domains\Cart\Models\Cart
+ * @mixin Cart
  */
 class CartResource extends JsonResource
 {
@@ -20,7 +21,7 @@ class CartResource extends JsonResource
             : collect();
 
         $subtotal = $items->reduce(
-            fn (float $carry, $item): float => $carry + ((float) ($item->variant?->product?->precio ?? 0) * $item->cantidad),
+            fn (float $carry, $item): float => $carry + ((float) ($item->buyable?->getPrice() ?? 0) * $item->cantidad),
             0.0,
         );