CVE-2026-103504: fallo de gravedad alta en Gitea

Changing an organization team's permission through the API with only the `permission` field did not rebuild the team's per-unit access, and the requested level was not applied as a cap. After an organization owner demoted a team, for example from admin to read, the team's members kept their previous unit permissions, including write access to the team's repositories. The web form was not affected.