update database

lib/features/cart/domain/entities/cart_item.dart

@@ -0,0 +1,98 @@
+/// Domain Entity: Cart Item
+///
+/// Represents a single item in a shopping cart.
+library;
+
+/// Cart Item Entity
+///
+/// Contains item-level information:
+/// - Product reference
+/// - Quantity
+/// - Pricing
+class CartItem {
+  /// Unique cart item identifier
+  final String cartItemId;
+
+  /// Cart ID this item belongs to
+  final String cartId;
+
+  /// Product ID
+  final String productId;
+
+  /// Quantity ordered
+  final double quantity;
+
+  /// Unit price at time of adding to cart
+  final double unitPrice;
+
+  /// Subtotal (quantity * unitPrice)
+  final double subtotal;
+
+  /// Timestamp when item was added
+  final DateTime addedAt;
+
+  const CartItem({
+    required this.cartItemId,
+    required this.cartId,
+    required this.productId,
+    required this.quantity,
+    required this.unitPrice,
+    required this.subtotal,
+    required this.addedAt,
+  });
+
+  /// Calculate subtotal (for verification)
+  double get calculatedSubtotal => quantity * unitPrice;
+
+  /// Copy with method for immutability
+  CartItem copyWith({
+    String? cartItemId,
+    String? cartId,
+    String? productId,
+    double? quantity,
+    double? unitPrice,
+    double? subtotal,
+    DateTime? addedAt,
+  }) {
+    return CartItem(
+      cartItemId: cartItemId ?? this.cartItemId,
+      cartId: cartId ?? this.cartId,
+      productId: productId ?? this.productId,
+      quantity: quantity ?? this.quantity,
+      unitPrice: unitPrice ?? this.unitPrice,
+      subtotal: subtotal ?? this.subtotal,
+      addedAt: addedAt ?? this.addedAt,
+    );
+  }
+
+  @override
+  bool operator ==(Object other) {
+    if (identical(this, other)) return true;
+
+    return other is CartItem &&
+        other.cartItemId == cartItemId &&
+        other.cartId == cartId &&
+        other.productId == productId &&
+        other.quantity == quantity &&
+        other.unitPrice == unitPrice &&
+        other.subtotal == subtotal;
+  }
+
+  @override
+  int get hashCode {
+    return Object.hash(
+      cartItemId,
+      cartId,
+      productId,
+      quantity,
+      unitPrice,
+      subtotal,
+    );
+  }
+
+  @override
+  String toString() {
+    return 'CartItem(cartItemId: $cartItemId, productId: $productId, '
+        'quantity: $quantity, unitPrice: $unitPrice, subtotal: $subtotal)';
+  }
+}