feat: Add quantity controls to cart with +/- buttons

src/pages/catalog.vue

@@ -17,6 +17,7 @@
             :currency="currency"
             @remove="removeFromCart"
             @checkout="goToCheckout"
+            @update-quantity="updateCartQuantity"
           />
         </div>
       </v-col>
@@ -98,6 +99,16 @@ export default {
         item.quantity = 0;
       }
     },
+    updateCartQuantity({ itemId, quantity }) {
+      const cartItem = this.cartItems.find(i => i.id === itemId);
+      if (cartItem) {
+        cartItem.quantity = quantity;
+      }
+      const productItem = this.items.find(i => i.id === itemId);
+      if (productItem) {
+        productItem.quantity = quantity;
+      }
+    },
     goToCheckout() {
       this.$router.push('/comprar');
     },