feat: meeting room locking

internal/events/meeting_voice.go

@@ -92,7 +92,12 @@ func tryCleanupTempChannel(s *discordgo.Session, ctx context.Context, svc *servi
 	}
 
 	// Check if anyone is still in the channel.
-	g, err := s.Guild(guildID)
+	// IMPORTANT: don't use REST `s.Guild(...)` here; it doesn't include VoiceStates.
+	// Use the session state cache (requires IntentsGuildVoiceStates).
+	if s == nil || s.State == nil {
+		return
+	}
+	g, err := s.State.Guild(guildID)
 	if err != nil || g == nil {
 		return
 	}