AVideo: Unauthenticated Access to Scheduler Plugin Endpoints Leaks Scheduled Tasks, Email Content, and User Mappings

WWBN AVideo is an open source video platform. In versions up to and including 26.0, three `list.json.php` endpoints in the Scheduler plugin lack any authentication check, while every other endpoint in the same plugin directories (`add.json.php`, `delete.json.php`, `index.php`) requires `User::isAdmin()`. An unauthenticated attacker can retrieve all scheduled tasks (including internal callback URLs and parameters), admin-composed email messages, and user-to-email targeting mappings by sending simple GET requests. Commit 83390ab1fa8dca2de3f8fa76116a126428405431 contains a patch.