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/index/index.tsx

@@ -4,6 +4,7 @@ import { useAuthStore } from '../../stores/auth';
 import { useHealthStore } from '../../stores/health';
 import EmptyState from '../../components/EmptyState';
 import Loading from '../../components/Loading';
+import { trackPageView } from '@/services/analytics';
 import './index.scss';
 
 export default function Index() {
@@ -13,6 +14,7 @@ export default function Index() {
   useDidShow(() => {
     restoreAuth();
     refreshToday();
+    trackPageView('home');
   });
 
   const hour = new Date().getHours();