AVideo's Missing Authorization in Playlist Schedule Creation Allows Cross-User Broadcast Hijacking

WWBN AVideo is an open source video platform. In versions up to and including 26.0, the `plugin/PlayLists/View/Playlists_schedules/add.json.php` endpoint allows any authenticated user with streaming permission to create or modify broadcast schedules targeting any playlist on the platform, regardless of ownership. When the schedule executes, the rebroadcast runs under the victim playlist owner's identity, allowing content hijacking and stream disruption. Commit 1e6dc20172de986f60641eb4fdb4090f079ffdce contains a patch.