重构: 手续费改为百分比/固定二选一，清理旧 Skin/Order/ShipLog 演示链路

手续费:
- 新增 fee_type 字段(rate/fixed)，百分比与固定金额二选一，不再叠加
- calculateServiceFee 按 fee_type 分支计算
- 商户创建/更新校验 fee_type，订单落库快照 fee_type
- 前端表单改为下拉选择手续费类型，动态显示对应输入框
- 测试拆为 TestFeeRate + TestFeeFixed

清理旧链路:
- 删除旧 Skin/Order/ShipLog 模型及 OrderService/SkinService
- Dashboard 迁移到 FulfillmentService
- 上游 /api/open/v1 改为基于 FulfillmentOrder 实现，接口契约不变
- 推送留痕改用 AuditLog，不再建 ShipLog 表
- 删除前端 Skins/Orders/ShipLogs/Distributors 页面及路由、菜单、API、类型
- 新增迁移 003: 添加 fee_type 列并 DROP 旧表

backend/internal/handler/order.go

@@ -1,8 +1,6 @@
 package handler
 
 import (
-	"strconv"
-
 	"affiliate_dash/internal/middleware"
 	"affiliate_dash/internal/model"
 	"affiliate_dash/internal/pkg/response"
@@ -11,126 +9,20 @@ import (
 	"github.com/gin-gonic/gin"
 )
 
-type OrderHandler struct {
-	svc *service.OrderService
+// DashboardHandler 仪表盘统计接口。
+type DashboardHandler struct {
+	svc *service.FulfillmentService
 }
 
-func NewOrderHandler(svc *service.OrderService) *OrderHandler {
-	return &OrderHandler{svc: svc}
+func NewDashboardHandler(svc *service.FulfillmentService) *DashboardHandler {
+	return &DashboardHandler{svc: svc}
 }
 
-func (h *OrderHandler) List(c *gin.Context) {
-	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
-	size, _ := strconv.Atoi(c.DefaultQuery("size", "20"))
-	q := service.OrderListQuery{
-		MerchantID: middleware.GetMerchantID(c),
-		Page:       page,
-		Size:       size,
-		Status:     c.Query("status"),
-	}
-	// 分销商只能看自己的订单
-	if middleware.GetRole(c) == model.RoleDistributor {
-		id := middleware.GetUserID(c)
-		q.DistributorID = &id
-	} else if d := c.Query("distributor_id"); d != "" {
-		id, _ := strconv.ParseUint(d, 10, 64)
-		uid := uint(id)
-		q.DistributorID = &uid
-	}
-	list, total, err := h.svc.List(q)
-	if err != nil {
-		response.ServerError(c, err.Error())
-		return
-	}
-	response.Page(c, list, total, page, size)
-}
-
-type createOrderReq struct {
-	SkinID        uint   `json:"skin_id" binding:"required"`
-	BuyerName     string `json:"buyer_name"`
-	Remark        string `json:"remark"`
-	Status        string `json:"status"`         // 管理员可指定初始状态（联调造异常单）
-	DistributorID *uint  `json:"distributor_id"` // 管理员可指定分销商
-}
-
-func (h *OrderHandler) Create(c *gin.Context) {
-	var req createOrderReq
-	if err := c.ShouldBindJSON(&req); err != nil {
-		response.BadRequest(c, "参数错误：请选择商品")
-		return
-	}
-	distributorID := middleware.GetUserID(c)
-	status := ""
-	// 管理员可指定分销商、任意初始状态（方便联调）
-	if middleware.GetRole(c) == model.RoleAdmin {
-		if req.DistributorID != nil && *req.DistributorID > 0 {
-			distributorID = *req.DistributorID
-		}
-		if d := c.Query("distributor_id"); d != "" {
-			id, _ := strconv.ParseUint(d, 10, 64)
-			distributorID = uint(id)
-		}
-		status = req.Status
-	}
-	if req.BuyerName == "" {
-		req.BuyerName = "测试买家"
-	}
-	order, err := h.svc.Create(service.CreateOrderInput{
-		MerchantID:    middleware.GetMerchantID(c),
-		SkinID:        req.SkinID,
-		DistributorID: distributorID,
-		BuyerName:     req.BuyerName,
-		Remark:        req.Remark,
-		Status:        status,
-	})
-	if err != nil {
-		response.BadRequest(c, err.Error())
-		return
-	}
-	response.OK(c, order)
-}
-
-type orderStatusReq struct {
-	Status string `json:"status" binding:"required"`
-}
-
-func (h *OrderHandler) UpdateStatus(c *gin.Context) {
-	id, _ := strconv.ParseUint(c.Param("id"), 10, 64)
-	var req orderStatusReq
-	if err := c.ShouldBindJSON(&req); err != nil {
-		response.BadRequest(c, "参数错误")
-		return
-	}
-	if err := h.svc.UpdateStatus(middleware.GetMerchantID(c), uint(id), req.Status); err != nil {
-		response.BadRequest(c, err.Error())
-		return
-	}
-	response.OK(c, nil)
-}
-
-func (h *OrderHandler) Dashboard(c *gin.Context) {
-	stats, err := h.svc.Dashboard(middleware.GetMerchantID(c))
+func (h *DashboardHandler) Dashboard(c *gin.Context) {
+	stats, err := h.svc.Dashboard(middleware.GetMerchantID(c), middleware.GetRole(c) == model.RoleAdmin)
 	if err != nil {
 		response.ServerError(c, err.Error())
 		return
 	}
 	response.OK(c, stats)
 }
-
-// ListShipLogs 发货推送记录（管理端）
-func (h *OrderHandler) ListShipLogs(c *gin.Context) {
-	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
-	size, _ := strconv.Atoi(c.DefaultQuery("size", "20"))
-	list, total, err := h.svc.ListShipLogs(service.ShipLogListQuery{
-		MerchantID: middleware.GetMerchantID(c),
-		Page:       page,
-		Size:       size,
-		OrderNo:    c.Query("order_no"),
-		ShipStatus: c.Query("ship_status"),
-	})
-	if err != nil {
-		response.ServerError(c, err.Error())
-		return
-	}
-	response.Page(c, list, total, page, size)
-}