Automated checking for uploads and git tags after DSA/DLA

(as discussed in the Debian LTS meeting 2025-01-23, this is an idea and not a task to be worked on without prior discussion)

Currently, it's easy to send an DSA/DLA without the respective package being in the archive. This can for example happen due to forgotten uploads, or build failures.

A tool should check every DSA/DLA after some delay (24h?) for:

• a package in the archive matching the listed name and version number
• a DEP-14 compatible git tag of that version when there's a packaging VCS listed in debian/control

And in the case of something missing notify the sender.