baostock drops a session after a few hundred queries; every later query
then returned 用户未登录 and the symbol failed. download_daily_batch now
refreshes the session every relogin_every symbols and re-logs in + retries
once on a detected session loss. akshare fallback now defaults off in the
batch path since it is slow/unreliable on this network and the re-login
keeps baostock as the fast primary.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Yuxuan Yan
419114b87b