feat: add CartController for cart state management

lib/src/controllers/cart_controller.dart

@@ -0,0 +1,91 @@
+import 'package:get/get.dart';
+import 'package:mom_kitchen/src/controllers/base/base_controller.dart';
+import 'package:mom_kitchen/src/controllers/home_controller.dart';
+
+class CartItem {
+  final ProductModel product;
+  int quantity;
+
+  CartItem({
+    required this.product,
+    this.quantity = 1,
+  });
+
+  double get totalPrice => product.price * quantity;
+}
+
+class CartController extends BaseController {
+  final cartItems = <CartItem>[].obs;
+
+  @override
+  void onInit() {
+    super.onInit();
+  }
+
+  void addProduct(ProductModel product) {
+    final index = cartItems.indexWhere((item) => item.product.name == product.name);
+    if (index >= 0) {
+      cartItems[index].quantity++;
+      cartItems.refresh();
+    } else {
+      cartItems.add(CartItem(product: product));
+    }
+  }
+
+  void removeProduct(String productName) {
+    cartItems.removeWhere((item) => item.product.name == productName);
+  }
+
+  void updateQuantity(String productName, int quantity) {
+    final index = cartItems.indexWhere((item) => item.product.name == productName);
+    if (index >= 0) {
+      if (quantity <= 0) {
+        cartItems.removeAt(index);
+      } else {
+        cartItems[index].quantity = quantity;
+        cartItems.refresh();
+      }
+    }
+  }
+
+  void incrementQuantity(String productName) {
+    final index = cartItems.indexWhere((item) => item.product.name == productName);
+    if (index >= 0) {
+      cartItems[index].quantity++;
+      cartItems.refresh();
+    }
+  }
+
+  void decrementQuantity(String productName) {
+    final index = cartItems.indexWhere((item) => item.product.name == productName);
+    if (index >= 0) {
+      if (cartItems[index].quantity > 1) {
+        cartItems[index].quantity--;
+        cartItems.refresh();
+      } else {
+        cartItems.removeAt(index);
+      }
+    }
+  }
+
+  void clearCart() {
+    cartItems.clear();
+  }
+
+  double get totalPrice {
+    return cartItems.fold(0.0, (sum, item) => sum + item.totalPrice);
+  }
+
+  int get totalItems {
+    return cartItems.fold(0, (sum, item) => sum + item.quantity);
+  }
+
+  bool isInCart(String productName) {
+    return cartItems.any((item) => item.product.name == productName);
+  }
+
+  int getQuantity(String productName) {
+    final index = cartItems.indexWhere((item) => item.product.name == productName);
+    return index >= 0 ? cartItems[index].quantity : 0;
+  }
+}