feat: Iteration 3 — 咨询轮询、统计概览、埋点后端

- consultation_service 支持 after_id 增量消息查询
- 小程序咨询详情页 8 秒轮询新消息
- 新增 DashboardStatsResp 综合统计端点 (/statistics/dashboard)
- 新增 /analytics/batch 埋点接收端点（日志记录模式）

apps/miniprogram/src/services/doctor.ts

@@ -122,7 +122,7 @@ export async function getSession(id: string) {
   return api.get<ConsultationSession>(`/health/consultation-sessions/${id}`);
 }
 
-export async function listMessages(sessionId: string, params?: { page?: number; page_size?: number }) {
+export async function listMessages(sessionId: string, params?: { page?: number; page_size?: number; after_id?: string }) {
   return api.get<{ data: ConsultationMessage[]; total: number }>(
     `/health/consultation-sessions/${sessionId}/messages`,
     params,