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/followup/detail/index.tsx

@@ -3,6 +3,7 @@ import { View, Text, Textarea } from '@tarojs/components';
 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 Loading from '../../../components/Loading';
 import ErrorState from '../../../components/ErrorState';
 import './index.scss';
@@ -41,6 +42,10 @@ export default function FollowUpDetail() {
         content: { text: content.trim() },
       });
       Taro.showToast({ title: '提交成功', icon: 'success' });
+      const tmplId = TEMPLATE_IDS.FOLLOWUP_REMINDER;
+      if (tmplId) {
+        try { await Taro.requestSubscribeMessage({ tmplIds: [tmplId] }); } catch { /* 用户拒绝 */ }
+      }
       setContent('');
     } catch {
       Taro.showToast({ title: '提交失败', icon: 'none' });