新增支付流程，新增支付页面等待倒计时，自动检查订单状态等

lib/app/model/entity_from_json_util.dart

@@ -43,6 +43,8 @@ abstract class EntityFromJsonUtil {
         return KRPurchaseOrderNo.fromJson(json) as T;
       case "KRPurchaseOrderUrl":
         return KRPurchaseOrderUrl.fromJson(json) as T;
+      case "KRCheckoutResponse":
+        return KRCheckoutResponse.fromJson(json) as T;
       case "KROrderStatus":
         return KROrderStatus.fromJson(json) as T;
       case "KRAlreadySubscribeList":

lib/app/model/response/kr_purchase_order_no.dart

@@ -18,4 +18,48 @@ class KRPurchaseOrderUrl {
   factory KRPurchaseOrderUrl.fromJson(Map<String, dynamic> json) {
     return KRPurchaseOrderUrl(url: json['checkout_url'] ?? '');
   }
+}
+
+/// Checkout 响应（参考 Tauri 项目）
+class KRCheckoutResponse {
+  final String type; // "url" | "qr" | "stripe"
+  final String? checkoutUrl;
+  final KRStripePayment? stripe;
+
+  KRCheckoutResponse({
+    required this.type,
+    this.checkoutUrl,
+    this.stripe,
+  });
+
+  factory KRCheckoutResponse.fromJson(Map<String, dynamic> json) {
+    return KRCheckoutResponse(
+      type: json['type'] ?? 'url',
+      checkoutUrl: json['checkout_url'],
+      stripe: json['stripe'] != null
+          ? KRStripePayment.fromJson(json['stripe'])
+          : null,
+    );
+  }
+}
+
+/// Stripe 支付信息
+class KRStripePayment {
+  final String method;
+  final String clientSecret;
+  final String publishableKey;
+
+  KRStripePayment({
+    required this.method,
+    required this.clientSecret,
+    required this.publishableKey,
+  });
+
+  factory KRStripePayment.fromJson(Map<String, dynamic> json) {
+    return KRStripePayment(
+      method: json['method'] ?? '',
+      clientSecret: json['client_secret'] ?? '',
+      publishableKey: json['publishable_key'] ?? '',
+    );
+  }
 }