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/services/analytics.ts

@@ -0,0 +1,82 @@
+import Taro from '@tarojs/taro';
+
+type EventName =
+  | 'page_view'
+  | 'login'
+  | 'bind_phone'
+  | 'health_data_input'
+  | 'health_trend_view'
+  | 'appointment_create'
+  | 'appointment_detail'
+  | 'followup_submit'
+  | 'report_view'
+  | 'article_view'
+  | 'article_share'
+  | 'medication_add'
+  | 'family_add'
+  | 'profile_edit';
+
+interface AnalyticsEvent {
+  event: EventName | string;
+  properties?: Record<string, unknown>;
+  timestamp: number;
+  userId?: string;
+  patientId?: string;
+}
+
+const QUEUE_KEY = 'analytics_queue';
+const MAX_QUEUE_SIZE = 50;
+
+function getQueue(): AnalyticsEvent[] {
+  return Taro.getStorageSync(QUEUE_KEY) || [];
+}
+
+function setQueue(queue: AnalyticsEvent[]): void {
+  Taro.setStorageSync(QUEUE_KEY, queue.slice(-MAX_QUEUE_SIZE));
+}
+
+export function trackEvent(event: EventName | string, properties?: Record<string, unknown>): void {
+  const userId = Taro.getStorageSync('user')?.id;
+  const patientId = Taro.getStorageSync('current_patient_id');
+
+  const evt: AnalyticsEvent = {
+    event,
+    properties,
+    timestamp: Date.now(),
+    userId,
+    patientId,
+  };
+
+  const queue = getQueue();
+  queue.push(evt);
+  setQueue(queue);
+}
+
+export function trackPageView(pageName: string, properties?: Record<string, unknown>): void {
+  trackEvent('page_view', { page: pageName, ...properties });
+}
+
+export async function flushEvents(): Promise<void> {
+  const queue = getQueue();
+  if (queue.length === 0) return;
+
+  const batch = queue.slice();
+  setQueue([]);
+
+  try {
+    const BASE_URL = process.env.TARO_APP_API_URL || 'http://localhost:3000/api/v1';
+    await Taro.request({
+      url: `${BASE_URL}/analytics/batch`,
+      method: 'POST',
+      data: { events: batch },
+    });
+  } catch {
+    // 发送失败，回填队列
+    const current = getQueue();
+    setQueue([...batch.slice(-MAX_QUEUE_SIZE + current.length), ...current]);
+  }
+}
+
+export function getQueueSize(): number {
+  return getQueue().length;
+}