Support Ubuntu 26.04 LTS (Resolute Raccoon)

Dokku is adding Ubuntu 26.04 LTS ("Resolute Raccoon", codename resolute) support - see dokku/dokku#8768. This project's .deb packages are published to the dokku/dokku PackageCloud repository, but the release-packagecloud-deb Makefile target only pushes to ubuntu/jammy and ubuntu/noble, not resolute. Please add an ubuntu/resolute push line mirroring ubuntu/noble and cut a release.