Change the package base name of the Go code, from
`git.blender.org/flamenco` to `projects.blender.org/studio/flamenco`.
The old location, `git.blender.org`, has no longer been use since the
[migration to Gitea][1]. The new package names now reflect the actual
location where Flamenco is hosted.
[1]: https://code.blender.org/2023/02/new-blender-development-infrastructure/
Workers can be soft-deleted, which means that they stay in the database.
As such, foreign key constraints `ON DELETE CASCADE` do not trigger, and
thus their sleep schedule can still be active. This is now detected and
handled gracefully.
