feat(miniprogram): 埋点事件追踪服务

- 新增 analytics.ts：trackEvent/trackPageView/flushEvents
- 事件队列本地缓存，批量上报到 /analytics/batch
- 首页 page_view、预约创建、随访提交、健康数据录入四个关键埋点

apps/miniprogram/src/pages/followup/detail/index.tsx

@@ -4,6 +4,7 @@ import Taro, { useRouter } from '@tarojs/taro';
 import { getTaskDetail, submitRecord } from '../../../services/followup';
 import type { FollowUpTask } from '../../../services/followup';
 import { TEMPLATE_IDS } from '@/services/wechat-templates';
+import { trackEvent } from '@/services/analytics';
 import Loading from '../../../components/Loading';
 import ErrorState from '../../../components/ErrorState';
 import './index.scss';
@@ -42,6 +43,7 @@ export default function FollowUpDetail() {
         content: { text: content.trim() },
       });
       Taro.showToast({ title: '提交成功', icon: 'success' });
+      trackEvent('followup_submit', { task_id: id });
       const tmplId = TEMPLATE_IDS.FOLLOWUP_REMINDER;
       if (tmplId) {
         try { await Taro.requestSubscribeMessage({ tmplIds: [tmplId] }); } catch { /* 用户拒绝 */ }