feat(miniprogram): 微信订阅消息引导 + 个人中心消息 badge 占位

- 新增 wechat-templates.ts 集中管理模板 ID
- 预约成功后引导用户订阅预约提醒
- 随访记录提交后引导订阅随访提醒
- 个人中心新增消息中心入口 + 未读数 badge（MVP 占位 unreadCount: 0）

apps/miniprogram/src/pages/appointment/create/index.tsx

@@ -3,6 +3,7 @@ import { View, Text, Input } from '@tarojs/components';
 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 StepIndicator from '../../../components/StepIndicator';
 import WeekCalendar from '../../../components/WeekCalendar';
 import './index.scss';
@@ -111,6 +112,13 @@ export default function AppointmentCreate() {
         reason: reason.trim() || undefined,
       });
       Taro.showToast({ title: '预约成功', icon: 'success' });
+      // 订阅消息引导
+      const tmplId = TEMPLATE_IDS.APPOINTMENT_REMINDER;
+      if (tmplId) {
+        try {
+          await Taro.requestSubscribeMessage({ tmplIds: [tmplId] });
+        } catch { /* 用户拒绝 */ }
+      }
       setTimeout(() => Taro.navigateBack(), 1500);
     } catch {
       Taro.showToast({ title: '预约失败', icon: 'none' });