Ship signup sheet, subscribe reminders, cover crop, and theme updates.

Wire real WeChat app config, prefer activity cover over posters, and add admin cover cropping for the home banner.

Co-authored-by: Cursor <cursoragent@cursor.com>

README.md

@@ -26,6 +26,8 @@ npm test             # 接口冒烟测试（使用临时数据库，不影响真
 | --- | --- |
 | `PORT` | 端口，默认 3000 |
 | `WX_APPID` / `WX_SECRET` | 配置后走真实 `code2session` 登录；不配置则为演示登录 |
+| `WX_SUBSCRIBE_TMPL_ID` | 可选，订阅消息模板 ID（也可在管理后台「提醒设置」里填） |
+| `WX_MINI_STATE` | 订阅消息跳转版本：`formal` / `trial` / `developer`，默认 formal |
 | `DB_FILE` | 数据文件路径，默认 `server/data/db.json` |
 | `UPLOAD_DIR` | 上传目录，默认 `server/public/uploads` |