feat: integrate quantity selector component into cart and product detail pages for enhanced functionality

src/app/features/store/pages/product-detail-page/product-detail-page.component.html

@@ -54,11 +54,8 @@
             <section class="product-detail__section">
               <div class="product-detail__purchase">
                 <app-quantity-selector
-                  [quantity]="quantity()"
+                  [(quantity)]="quantity"
                   [max]="selectedVariant()?.stock ?? 1"
-                  (increase)="increaseQuantity()"
-                  (decrease)="decreaseQuantity()"
-                  (quantityChange)="quantity.set($event)"
                 />
 
                 <div class="product-detail__actions">

src/app/features/store/pages/product-detail-page/product-detail-page.component.ts

@@ -215,14 +215,7 @@ export class ProductDetailPageComponent implements OnInit, OnDestroy {
     }
   }
 
-  protected increaseQuantity(): void {
-    const currentStock = this.selectedVariant()?.stock ?? 1;
-    this.quantity.update((current) => current < currentStock ? current + 1 : current);
-  }
 
-  protected decreaseQuantity(): void {
-    this.quantity.update((current) => Math.max(1, current - 1));
-  }
 
   protected addToCart(): void {
     const variant = this.selectedVariant();