TikTok: return the video file and all carousel slides for external posts

For TikTok accounts (Business app lane), mediaItems on external posts currently carries only a thumbnail for videos and only the cover image for photo carousels (e.g. one image for a post that has 7 slides).

We analyse a creator's own posts with an AI model (what the video shows and says, the text on each slide) so we can understand the comments under them. For that we need the actual media:

• Videos: a downloadable URL to the video file (even a short-lived signed URL is fine; we download it right away and do not store or re-host it).

• Photo carousels: the URL of every slide, in order (and ideally the background music track).

Today we have to use a third-party scraper for this on TikTok, while on Instagram Zernio's mediaItems already give us downloadable video files and every carousel slide. Having the same on TikTok would let us use Zernio as the single source for all platforms.