[功能] 通过分割邮件原文来存储过大的邮件

Please describe your feature. The current solution has a problem that TG notifies when processing large emails, but the emails cannot be queried. By querying the logs, we can see the database insertion error: save email error Error: D1_ERROR: string or blob too big: SQLITE_TOOBIG. It can be seen that the failure to store the data is due to the blob/string being too large.