feat: 完成仪表盘和导出功能

- DashboardController: 实现完整的后端API
  - /api/dashboard - 仪表盘数据
  - /api/dashboard/kpis - KPI统计
  - /api/dashboard/activities - 活动摘要
  - /api/dashboard/todos - 待办事项
  - /api/dashboard/export - 导出CSV
  - /api/dashboard/kpis/export - KPI导出
  - /api/dashboard/activities/export - 活动导出

- dashboard.ts: 前端服务
  - 完整的API调用封装
  - 导出功能支持
  - 下载工具函数

- 更新任务状态:
  - TASK-401-405: 仪表盘模块100%
  - TASK-501-502: 单元测试

Co-authored-by: Claude <noreply@anthropic.com>

frontend/admin/src/services/dashboard.ts

@@ -103,9 +103,58 @@ export async function getTodos(): Promise<Todo[]> {
   return response.data.data
 }
 
+/**
+ * 导出仪表盘数据
+ */
+export async function exportDashboard(format: string = 'csv'): Promise<Blob> {
+  const response = await dashboardApi.get('/dashboard/export', {
+    params: { format },
+    responseType: 'blob'
+  })
+  return response as unknown as Blob
+}
+
+/**
+ * 导出KPI数据
+ */
+export async function exportKpis(): Promise<Blob> {
+  const response = await dashboardApi.get('/dashboard/kpis/export', {
+    responseType: 'blob'
+  })
+  return response as unknown as Blob
+}
+
+/**
+ * 导出活动数据
+ */
+export async function exportActivities(): Promise<Blob> {
+  const response = await dashboardApi.get('/dashboard/activities/export', {
+    responseType: 'blob'
+  })
+  return response as unknown as Blob
+}
+
+/**
+ * 下载文件工具函数
+ */
+export function downloadBlob(blob: Blob, filename: string) {
+  const url = window.URL.createObjectURL(blob)
+  const link = document.createElement('a')
+  link.href = url
+  link.download = filename
+  document.body.appendChild(link)
+  link.click()
+  document.body.removeChild(link)
+  window.URL.revokeObjectURL(url)
+}
+
 export default {
   getDashboard,
   getKpis,
   getActivitySummary,
-  getTodos
+  getTodos,
+  exportDashboard,
+  exportKpis,
+  exportActivities,
+  downloadBlob
 }