feat: 实现出差申请页面

- 创建出差申请表单，包含出差事由、行程明细、审批人选择
- 实现行程明细的增删改功能，支持开始/结束时间、出发地、目的地等
- 添加单程/往返类型选择和交通工具下拉选择
- 实现自动计算行程时长和总时长
- 创建审批人和抄送人选择页面
- 添加前后端API接口定义
- 更新i18n国际化翻译
- 整理开发文档和UI设计图

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/services/business-trip.ts

@@ -0,0 +1,85 @@
+import { api } from './api'
+
+// 出差申请接口类型定义
+export interface BusinessTripItinerary {
+  startTime: string
+  endTime: string
+  departure?: string
+  destination: string
+  transport?: string
+  tripType?: 'oneway' | 'roundtrip'
+  remark?: string
+}
+
+export interface CreateBusinessTripDto {
+  reason: string
+  itineraries: BusinessTripItinerary[]
+  approvers: number[]
+  cc_users?: number[]
+}
+
+export interface BusinessTripItem {
+  id: number
+  user_id: number
+  user_name: string
+  reason: string
+  start_date: string
+  end_date: string
+  duration: number
+  status: 'draft' | 'pending' | 'approved' | 'rejected' | 'cancelled'
+  approval_order_id: number | null
+  created_at: string
+  updated_at: string
+}
+
+export interface BusinessTripDetail extends BusinessTripItem {
+  itineraries: BusinessTripItinerary[]
+  approvers: ApproverInfo[]
+  cc_users: ApproverInfo[]
+}
+
+export interface ApproverInfo {
+  id: number
+  name: string
+  avatar?: string
+  position?: string
+}
+
+// 出差申请 API
+export const businessTripApi = {
+  // 创建出差申请
+  create: (data: CreateBusinessTripDto) =>
+    api.post('/business-trip', data),
+
+  // 获取出差列表
+  getList: (params?: { status?: string; page?: number; page_size?: number }) =>
+    api.get<BusinessTripItem[]>('/business-trip', { params }),
+
+  // 获取出差详情
+  getDetail: (id: number) =>
+    api.get<BusinessTripDetail>(`/business-trip/${id}`),
+
+  // 更新出差申请（草稿状态）
+  update: (id: number, data: Partial<CreateBusinessTripDto>) =>
+    api.put(`/business-trip/${id}`, data),
+
+  // 提交审批
+  submit: (id: number) =>
+    api.post(`/business-trip/${id}/submit`),
+
+  // 撤销申请
+  cancel: (id: number) =>
+    api.post(`/business-trip/${id}/cancel`),
+
+  // 获取用户列表（用于选择审批人和抄送）
+  getUsers: (params?: { search?: string }) =>
+    api.get<ApproverInfo[]>('/users', { params }),
+
+  // 保存草稿
+  saveDraft: (data: CreateBusinessTripDto) =>
+    api.post('/business-trip/draft', data),
+
+  // 获取草稿
+  getDrafts: () =>
+    api.get<BusinessTripItem[]>('/business-trip/drafts'),
+}