Applies brand colours and/or a logo from a brand kit to the video.
Scope is controlled by the flags: applyColors and applyLogo choose what is applied, allSlides whether it covers the whole video or just activeSlideId. persist decides whether the result is saved — with persist false the modified video is computed and returned without being written, which is how the editor previews the change.
Brand kits are plan-gated; the kit must belong to the caller's workspace.