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

frontend/src/api/index.ts

@@ -10,10 +10,7 @@ import type {
   Merchant,
   MerchantMember,
   MerchantProduct,
-  Order,
   PageResult,
-  ShipLog,
-  Skin,
   User,
   WalletAccount,
   WalletLedgerEntry,
@@ -39,33 +36,6 @@ export const dashboardApi = {
     request.get('/dashboard').then((r) => r.data.data as DashboardStats),
 }
 
-export const skinApi = {
-  list: (params?: Record<string, unknown>) =>
-    request.get('/skins', { params }).then((r) => r.data.data as PageResult<Skin>),
-  get: (id: number) =>
-    request.get(`/skins/${id}`).then((r) => r.data.data as Skin),
-  create: (data: Partial<Skin>) =>
-    request.post('/skins', data).then((r) => r.data.data as Skin),
-  update: (id: number, data: Partial<Skin>) =>
-    request.put(`/skins/${id}`, data).then((r) => r.data.data),
-  remove: (id: number) =>
-    request.delete(`/skins/${id}`).then((r) => r.data.data),
-}
-
-export const orderApi = {
-  list: (params?: Record<string, unknown>) =>
-    request.get('/orders', { params }).then((r) => r.data.data as PageResult<Order>),
-  create: (data: {
-    skin_id: number
-    buyer_name?: string
-    remark?: string
-    status?: string
-    distributor_id?: number
-  }) => request.post('/orders', data).then((r) => r.data.data as Order),
-  updateStatus: (id: number, status: string) =>
-    request.patch(`/orders/${id}/status`, { status }).then((r) => r.data.data),
-}
-
 export const userApi = {
   list: (params?: Record<string, unknown>) =>
     request.get('/users', { params }).then((r) => r.data.data as PageResult<User>),
@@ -75,11 +45,6 @@ export const userApi = {
     request.patch(`/users/${id}/status`, { status }).then((r) => r.data.data),
 }
 
-export const shipLogApi = {
-  list: (params?: Record<string, unknown>) =>
-    request.get('/ship-logs', { params }).then((r) => r.data.data as PageResult<ShipLog>),
-}
-
 export const merchantApi = {
   current: () =>
     request.get('/merchant').then((r) => r.data.data as { merchant: Merchant; role: MerchantMember['role'] }),
@@ -132,8 +97,17 @@ export const platformApi = {
     name: string
     contact_name?: string
     contact_info?: string
-    owner_user_id: number
+    owner_user_id?: number
+    owner_username?: string
+    owner_password?: string
+    owner_nickname?: string
+    features?: string
+    fee_type?: 'rate' | 'fixed'
+    fee_rate_bp?: number
+    fee_fixed_amount?: number
   }) => request.post('/platform/merchants', data).then((r) => r.data.data as Merchant),
+  updateMerchant: (id: number, data: Partial<Merchant>) =>
+    request.patch(`/platform/merchants/${id}`, data).then((r) => r.data.data),
   addMember: (
     merchantId: number,
     data: { user_id: number; role: MerchantMember['role']; is_default?: boolean },