feat: 实现订单支付功能模块

- 新增订单管理、支付回调、购买验证等核心服务
- 实现订单、订单项目的数据存储层和 API 接口
- 添加订单数据库迁移和 DTO 定义
- 更新 API 文档和路由配置
- 同步 3 个新规范到主规范库（订单管理、订单支付、套餐购买验证）
- 完成 OpenSpec 变更归档

Ultraworked with Sisyphus

internal/handler/callback/payment.go

@@ -0,0 +1,60 @@
+package callback
+
+import (
+	"github.com/gofiber/fiber/v2"
+
+	"github.com/break/junhong_cmp_fiber/internal/model"
+	orderService "github.com/break/junhong_cmp_fiber/internal/service/order"
+	"github.com/break/junhong_cmp_fiber/pkg/errors"
+	"github.com/break/junhong_cmp_fiber/pkg/response"
+)
+
+type PaymentHandler struct {
+	orderService *orderService.Service
+}
+
+func NewPaymentHandler(orderService *orderService.Service) *PaymentHandler {
+	return &PaymentHandler{orderService: orderService}
+}
+
+type WechatPayCallbackRequest struct {
+	OrderNo string `json:"order_no" xml:"out_trade_no"`
+}
+
+func (h *PaymentHandler) WechatPayCallback(c *fiber.Ctx) error {
+	var req WechatPayCallbackRequest
+	if err := c.BodyParser(&req); err != nil {
+		return errors.New(errors.CodeInvalidParam, "请求参数解析失败")
+	}
+
+	if req.OrderNo == "" {
+		return errors.New(errors.CodeInvalidParam, "订单号不能为空")
+	}
+
+	if err := h.orderService.HandlePaymentCallback(c.UserContext(), req.OrderNo, model.PaymentMethodWechat); err != nil {
+		return err
+	}
+
+	return response.Success(c, map[string]string{"return_code": "SUCCESS"})
+}
+
+type AlipayCallbackRequest struct {
+	OrderNo string `json:"out_trade_no" form:"out_trade_no"`
+}
+
+func (h *PaymentHandler) AlipayCallback(c *fiber.Ctx) error {
+	var req AlipayCallbackRequest
+	if err := c.BodyParser(&req); err != nil {
+		return errors.New(errors.CodeInvalidParam, "请求参数解析失败")
+	}
+
+	if req.OrderNo == "" {
+		return errors.New(errors.CodeInvalidParam, "订单号不能为空")
+	}
+
+	if err := h.orderService.HandlePaymentCallback(c.UserContext(), req.OrderNo, model.PaymentMethodAlipay); err != nil {
+		return err
+	}
+
+	return c.SendString("success")
+}