Fix debian/changelog, remove unneeded debian files

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Date:      Fri Jan 9 19:24:12 2026 +0100
# Committer: Joe User <joe@rpi4b.lan>
#
# On branch master
# Your branch is ahead of 'origin/master' by 2 commits.
#   (use "git push" to publish your local commits)
#
# Changes to be committed:
#	deleted:    debian/README.Debian
#	deleted:    debian/README.source
#	deleted:    debian/backup-docs.docs
#	deleted:    debian/backup.cron.d.ex
#	deleted:    debian/backup.doc-base.ex
#	modified:   debian/changelog
#	deleted:    debian/manpage.1.ex
#	deleted:    debian/manpage.md.ex
#	deleted:    debian/manpage.sgml.ex
#	deleted:    debian/manpage.xml.ex
#	deleted:    debian/postinst.ex
#	deleted:    debian/postrm.ex
#	deleted:    debian/preinst.ex
#	deleted:    debian/prerm.ex
#	deleted:    debian/salsa-ci.yml.ex
#	deleted:    debian/source/format
#	deleted:    debian/upstream/metadata.ex
#	deleted:    debian/watch.ex
#
