Cancelled pretalx session became unmanaged #97
Description
Session #2025-KalpaDesktop:seagl.org was cancelled in pretalx and should have been moved by Patch into subspace #SeaGL2025-UnscheduledSessions, but instead became unmanaged and erroneously remained in #SeaGL2025-UpcomingSessions.
Ensure Patch has visibility of cancelled events or use heuristics to infer them.