refactor: restructure rpm repo path to distro/version/arch layout

Move from /var/www/rpm/mistralrs/fedora-43/x86_64/ to
/var/www/rpm/fedora/43/x86_64/ so the repo can host packages
from multiple projects under a conventional hierarchy.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

script/publish-repo.sh

@@ -2,7 +2,7 @@
 set -euo pipefail
 
 RPM_DIR="${1:?usage: $0 <rpm-directory>}"
-REMOTE_DIR="/var/www/rpm/mistralrs/fedora-43/x86_64"
+REMOTE_DIR="/var/www/rpm/fedora/43/x86_64"
 
 # sign each rpm with the imported gpg key
 for rpm in "${RPM_DIR}"/*.rpm; do