CVE-2026-34374: AVideo has SQL Injection in Live_schedule::keyExists() via Unparameterized Stream Key

WWBN AVideo is an open source video platform. In versions up to and including 26.0, the `Live_schedule::keyExists()` method constructs a SQL query by interpolating a stream key directly into the query string without parameterization. This method is called as a fallback from `LiveTransmition::keyExists()` when the initial parameterized lookup returns no results. Although the calling function correctly uses parameterized queries for its own lookup, the fallback path to `Live_schedule::keyExists()` undoes this protection entirely. This vulnerability is distinct from GHSA-pvw4-p2jm-chjm, which covers SQL injection via the `live_schedule_id` parameter in the reminder function. This finding targets the stream key lookup path used during RTMP publish authentication. As of time of publication, no patched versions are available.