refactor(product-row-card): move variant selection logic into constructor for better clarity

src/app/shared/components/product-row-card/product-row-card.component.ts

@@ -27,7 +27,12 @@ export class ProductRowCardComponent {
   readonly quantity = model<number>(1);
   readonly selectedVariant = model<any>(null);
 
-  private readonly selectFirstVariant = effect(() => {
+  // Interactive events
+  readonly buy = output<void>();
+  readonly addToCart = output<{ quantity: number; variant: any }>();
+
+  constructor() {
+    effect(() => {
       const variants = this.variants();
       const selectedVariant = this.selectedVariant();
 
@@ -38,10 +43,7 @@ export class ProductRowCardComponent {
         this.selectedVariant.set(variants[0].value);
       }
     });
-
-  // Interactive events
-  readonly buy = output<void>();
-  readonly addToCart = output<{ quantity: number; variant: any }>();
+  }
 
   // Formatted string for price: "$ 10.000"
   readonly formattedPrice = computed(() => {