HTTP client for IServ school platforms. Log in to an IServ instance (e.g. https://grabbe-dt.de) and fetch common student data like unread mail counts, calendar events, files/folders, tasks/exercises, announcements/news, and other IServ modules via HTTP endpoints. Includes best-effort file ops + exercise submission.

适用于IServ学校平台的HTTP客户端。登录IServ实例（例如https://grabbe-dt.de），通过HTTP端点获取学生常用数据，如未读邮件数量、日历事件、文件夹与文件、任务与练习、公告与新闻及其他IServ模块。支持尽力而为的文件操作和作业提交。