feat(reports): 企业合规报表（后端聚合 + CSV 导出 + 前端页面） (#82)

新增合规报表：ReportService 逐任务聚合备份合规证据（成功率/最近成功/SLA 判定/加密/受保护量）+ JSON/CSV API；前端新增 /reports 页面（汇总卡片+明细表+CSV 导出）。后端 go test、前端 tsc+vite、端到端路由验证均通过。

server/internal/app/app.go

@@ -104,6 +104,7 @@ func New(ctx context.Context, cfg config.Config, version string) (*Application,
 	restoreRecordRepo := repository.NewRestoreRecordRepository(db)
 	restoreLogHub := backup.NewLogHub()
 	dashboardService := service.NewDashboardService(backupTaskRepo, backupRecordRepo, storageTargetRepo)
+	reportService := service.NewReportService(backupTaskRepo, backupRecordRepo)
 	settingsService := service.NewSettingsService(systemConfigRepo)
 
 	// Audit
@@ -268,6 +269,7 @@ func New(ctx context.Context, cfg config.Config, version string) (*Application,
 		ApiKeyService:            apiKeyService,
 		NotificationService:      notificationService,
 		DashboardService:         dashboardService,
+		ReportService:            reportService,
 		SettingsService:          settingsService,
 		NodeService:              nodeService,
 		AgentService:             agentService,