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/service/merchant.go

@@ -11,6 +11,7 @@ import (
 
 	"affiliate_dash/internal/model"
 
+	"golang.org/x/crypto/bcrypt"
 	"gorm.io/gorm"
 	"gorm.io/gorm/clause"
 )
@@ -28,38 +29,60 @@ func NewMerchantService(db *gorm.DB, codec *SecretCodec, tenant *TenantService)
 }
 
 type CreateMerchantInput struct {
-	Code        string
-	Name        string
-	ContactName string
-	ContactInfo string
-	OwnerUserID uint
+	Code           string
+	Name           string
+	ContactName    string
+	ContactInfo    string
+	OwnerUserID    uint
+	OwnerUsername  string
+	OwnerPassword  string
+	OwnerNickname  string
+	Features       string
+	FeeType        string
+	FeeRateBP      int64
+	FeeFixedAmount int64
 }
 
 func (s *MerchantService) CreateMerchant(in CreateMerchantInput, actorUserID uint) (*model.Merchant, error) {
 	in.Code = strings.ToLower(strings.TrimSpace(in.Code))
 	in.Name = strings.TrimSpace(in.Name)
+	in.Features = NormalizeMerchantFeatures(in.Features)
 	if !merchantCodePattern.MatchString(in.Code) {
 		return nil, errors.New("商户编码需为 3-64 位小写字母、数字或连字符")
 	}
 	if in.Name == "" {
 		return nil, errors.New("商户名称不能为空")
 	}
-	if in.OwnerUserID == 0 {
+	if in.OwnerUserID == 0 && strings.TrimSpace(in.OwnerUsername) == "" {
 		return nil, errors.New("商户负责人不能为空")
 	}
+	if in.FeeRateBP < 0 || in.FeeRateBP > 10000 {
+		return nil, errors.New("手续费比例需在 0-10000 BP 之间")
+	}
+	if in.FeeFixedAmount < 0 {
+		return nil, errors.New("固定手续费不能小于零")
+	}
+	feeType := in.FeeType
+	if feeType == "" {
+		feeType = model.FeeTypeRate
+	}
+	if feeType != model.FeeTypeRate && feeType != model.FeeTypeFixed {
+		return nil, errors.New("手续费类型仅支持 rate 或 fixed")
+	}
 	merchant := &model.Merchant{
-		Code:        in.Code,
-		Name:        in.Name,
-		Status:      model.MerchantStatusActive,
-		ContactName: in.ContactName,
-		ContactInfo: in.ContactInfo,
+		Code:           in.Code,
+		Name:           in.Name,
+		Status:         model.MerchantStatusActive,
+		ContactName:    in.ContactName,
+		ContactInfo:    in.ContactInfo,
+		Features:       in.Features,
+		FeeType:        feeType,
+		FeeRateBP:      in.FeeRateBP,
+		FeeFixedAmount: in.FeeFixedAmount,
 	}
 	err := s.db.Transaction(func(tx *gorm.DB) error {
-		var owner model.User
-		if err := tx.First(&owner, in.OwnerUserID).Error; err != nil {
-			if errors.Is(err, gorm.ErrRecordNotFound) {
-				return errors.New("商户负责人不存在")
-			}
+		owner, err := s.resolveOrCreateOwner(tx, in)
+		if err != nil {
 			return err
 		}
 		if owner.Status != 1 {
@@ -88,6 +111,121 @@ func (s *MerchantService) CreateMerchant(in CreateMerchantInput, actorUserID uin
 	return merchant, nil
 }
 
+func (s *MerchantService) resolveOrCreateOwner(tx *gorm.DB, in CreateMerchantInput) (*model.User, error) {
+	if in.OwnerUserID != 0 {
+		var owner model.User
+		if err := tx.First(&owner, in.OwnerUserID).Error; err != nil {
+			if errors.Is(err, gorm.ErrRecordNotFound) {
+				return nil, errors.New("商户负责人不存在")
+			}
+			return nil, err
+		}
+		return &owner, nil
+	}
+	username := strings.TrimSpace(in.OwnerUsername)
+	password := strings.TrimSpace(in.OwnerPassword)
+	nickname := strings.TrimSpace(in.OwnerNickname)
+	if username == "" || len(username) < 3 {
+		return nil, errors.New("负责人用户名至少 3 位")
+	}
+	if len(password) < 6 {
+		return nil, errors.New("负责人密码至少 6 位")
+	}
+	if nickname == "" {
+		nickname = username
+	}
+	var count int64
+	if err := tx.Model(&model.User{}).Where("username = ?", username).Count(&count).Error; err != nil {
+		return nil, err
+	}
+	if count > 0 {
+		return nil, errors.New("负责人用户名已存在")
+	}
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return nil, err
+	}
+	owner := &model.User{
+		Username:     username,
+		PasswordHash: string(hash),
+		Nickname:     nickname,
+		Role:         model.RoleMerchant,
+		Status:       1,
+	}
+	if err := tx.Create(owner).Error; err != nil {
+		return nil, err
+	}
+	return owner, nil
+}
+
+type UpdateMerchantSettingsInput struct {
+	Name           *string
+	Status         *string
+	ContactName    *string
+	ContactInfo    *string
+	Features       *string
+	FeeType        *string
+	FeeRateBP      *int64
+	FeeFixedAmount *int64
+}
+
+func (s *MerchantService) UpdateMerchantSettings(merchantID uint, in UpdateMerchantSettingsInput, actorUserID uint) error {
+	updates := map[string]interface{}{}
+	if in.Name != nil {
+		name := strings.TrimSpace(*in.Name)
+		if name == "" {
+			return errors.New("商户名称不能为空")
+		}
+		updates["name"] = name
+	}
+	if in.Status != nil {
+		if *in.Status != model.MerchantStatusActive && *in.Status != model.MerchantStatusDisabled {
+			return errors.New("无效的商户状态")
+		}
+		updates["status"] = *in.Status
+	}
+	if in.ContactName != nil {
+		updates["contact_name"] = strings.TrimSpace(*in.ContactName)
+	}
+	if in.ContactInfo != nil {
+		updates["contact_info"] = strings.TrimSpace(*in.ContactInfo)
+	}
+	if in.Features != nil {
+		updates["features"] = NormalizeMerchantFeatures(*in.Features)
+	}
+	if in.FeeRateBP != nil {
+		if *in.FeeRateBP < 0 || *in.FeeRateBP > 10000 {
+			return errors.New("手续费比例需在 0-10000 BP 之间")
+		}
+		updates["fee_rate_bp"] = *in.FeeRateBP
+	}
+	if in.FeeFixedAmount != nil {
+		if *in.FeeFixedAmount < 0 {
+			return errors.New("固定手续费不能小于零")
+		}
+		updates["fee_fixed_amount"] = *in.FeeFixedAmount
+	}
+	if in.FeeType != nil {
+		if *in.FeeType != model.FeeTypeRate && *in.FeeType != model.FeeTypeFixed {
+			return errors.New("手续费类型仅支持 rate 或 fixed")
+		}
+		updates["fee_type"] = *in.FeeType
+	}
+	if len(updates) == 0 {
+		return errors.New("没有可更新字段")
+	}
+	return s.db.Transaction(func(tx *gorm.DB) error {
+		result := tx.Model(&model.Merchant{}).Where("id = ?", merchantID).Updates(updates)
+		if result.Error != nil {
+			return result.Error
+		}
+		if result.RowsAffected == 0 {
+			return errors.New("商户不存在")
+		}
+		return writeAudit(tx, &merchantID, &actorUserID, nil, "merchant.settings.update", "merchant", fmt.Sprint(merchantID), updates)
+	})
+}
+
 func (s *MerchantService) ListMerchants(page, size int) ([]model.Merchant, int64, error) {
 	page, size = normalizePage(page, size)
 	tx := s.db.Model(&model.Merchant{})