yum-utils (edit: and
Since a yum repository is just a directory that you run
createrepo(8) against and serve over http, functions you mention like uploading, keeping old versions around etc can be done with your usual tools like the shell, ssh, rsync etc. Or are you after a kind of attractive web-based method of managing a repo? I'm not sure if one exists.
As for updating metadata automatically, perhaps just use cron? Really, if these are your own packages then you should have tested the rpm before placing it in the repo, so having something check automatically if a rpm is invalid might not be needed, but again a regular cron job with
rpm --test could tell you.
I'm probably missing some great tools but this has worked for me for our limited needs for years.