feat: enable color selection for cart items and enhance UI integration

- Added `selected_color` field to `CartItem` model with migration
- Updated color swatch behavior on product detail page with selection logic and disabled button handling
- Improved cart templates to display selected color alongside item details
- Modified `add_item_to_cart` service and `add` view to handle color selection
- Enhanced styles for active swatches and cart item color display

static/css/cart.css

@@ -67,6 +67,13 @@
     line-height: 1.1;
 }
 
+.cart-item__color {
+    display: block;
+    color: #63768d;
+    font-size: 14px;
+    margin-top: 4px;
+}
+
 .cart-item__price {
     margin-top: 24px;
     color: var(--dark);

static/css/catalog.css

@@ -491,10 +491,14 @@ aside {
     height: 46px;
     border-radius: 50%;
     display: block;
+    border: 2px solid rgba(54, 33, 62, 0.18);
+    cursor: pointer;
+    transition: box-shadow 0.15s, border-color 0.15s;
 }
 
 .product-summary__swatch--active {
     box-shadow: 0 0 0 2px #ffffff, 0 0 0 4px #554971;
+    border-color: #554971;
 }
 
 .product-summary__description {