List tags used by an account

**Describe the problem to be solved**

I'm trying to have a full list of the tags a specific peertube user used on it's videos, using the API.

Correct me if I'm wrong, but at the moment it seems that the only way to do this is to list the videos of the user, then fetch detailed infos for each of them to check the tags.

**Describe the solution you would like:**

It would be nice to either have an API entry to list tags of an instance, tags used by a specific user. Or simply add the tags list to the videos infos returned when requesting the list of videos of a user.
The second option might be preferable, since it should be fairly easy to implement (I imagine, but maybe I'm wrong :/) and not adding complexity to the API.

Thanks for the great software :)

Start by reviewing the PeerTube API endpoint that lists videos for an account and how video details expose tags. Compare the two proposed approaches: a dedicated account-tag endpoint or including tags in video-list responses. Done means the chosen API behavior returns the tags used by a specific account and is documented or covered by the relevant API checks.

Written by the indexing model from the issue text.