fix(storefront): composition audit fixes for cart, catalog, product, compare, wishlist, static pages

- Replace hand-rolled loading/error/empty markup with shared app-skeleton,
  app-empty-state, and app-button across catalog, product details, cart,
  compare, wishlist, and the public static-page renderer
- Fix hardcoded hex colors that bypassed theme CSS variables (catalog,
  product details), restoring multi-tenant theme correctness
- Remove ~1100 lines of dead "alt" cart theme CSS (never applied by the
  template) from cart.component.scss, bringing it back under the 40kB
  build budget (89.49kB -> 59.39kB cart-component chunk)
- Swap legacy global .btn/.btn-ghost/.btn-primary classes for app-button
  in compare and wishlist empty/toolbar actions

src/app/pages/cart/cart.component.html

@@ -11,12 +11,12 @@
 
   @if (itemCount() === 0) {
     <div class="empty-cart">
-      <div class="empty-icon">
-        <app-icon name="cart" [size]="64" />
-      </div>
-      <h2>{{ 'cart.empty' | translate }}</h2>
-      <p>{{ 'cart.emptyDesc' | translate }}</p>
-      <a [routerLink]="'/' | langRoute" class="shop-btn">{{ 'cart.goShopping' | translate }}</a>
+      <app-empty-state [title]="'cart.empty' | translate" [description]="'cart.emptyDesc' | translate">
+        <app-icon slot="icon" name="cart" [size]="64" />
+        <div slot="actions">
+          <app-button variant="primary" [routerLink]="'/' | langRoute">{{ 'cart.goShopping' | translate }}</app-button>
+        </div>
+      </app-empty-state>
     </div>
   }