@spec clean(Keyword.t()) :: {:ok, [Mobilizon.Medias.Media.t()]}

Clean orphan media

Remove media that is not attached to an entity, such as media uploads that were never used in entities.

Options:

• grace_period how old in hours can the media be before it's taken into account for deletion
• dry_run just return the media that would have been deleted, don't actually delete it