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/appointment/create/index.tsx

@@ -4,6 +4,7 @@ import Taro from '@tarojs/taro';
 import { listDoctors, createAppointment, calendarView } from '../../../services/appointment';
 import { useAuthStore } from '../../../stores/auth';
 import { TEMPLATE_IDS } from '@/services/wechat-templates';
+import { trackEvent } from '@/services/analytics';
 import StepIndicator from '../../../components/StepIndicator';
 import WeekCalendar from '../../../components/WeekCalendar';
 import './index.scss';
@@ -112,6 +113,7 @@ export default function AppointmentCreate() {
         reason: reason.trim() || undefined,
       });
       Taro.showToast({ title: '预约成功', icon: 'success' });
+      trackEvent('appointment_create', { doctor_id: selectedDoctor.id, date: appointmentDate });
       // 订阅消息引导
       const tmplId = TEMPLATE_IDS.APPOINTMENT_REMINDER;
       if (tmplId) {