feat(cart): update cart layout styles for improved responsiveness and structure

src/app/shared/components/cart/cart.component.html

@@ -1,5 +1,5 @@
 <section
-  class="d-flex flex-column h-100 overflow-hidden text-secondary"
+  class="d-flex flex-column overflow-hidden text-secondary cart-shell"
   [style.background-color]="backgroundColor()"
 >
   <header class="d-flex align-items-center p-3 justify-content-between bg-transparent cart-header">

src/app/shared/components/cart/cart.component.scss

@@ -1,7 +1,15 @@
 :host {
-  display: block;
+  display: flex;
   width: 100%;
-  height: 100%;
+  min-height: 0;
+  max-height: 100%;
+  overflow: hidden;
+}
+
+.cart-shell {
+  flex: 1 1 auto;
+  min-height: 0;
+  max-height: 100%;
 }
 
 .cart-header {