- ChatChannelType.GRUPPE: created by Leitungsteam (any KC) or a Gemeinde Verantwortliche/r (own KC), mixing team users and guests/Konfis as explicit ChatParticipant rows (unlike GEMEINDE_GRUPPE, membership is not derived from Gemeinde) - POST /chat/:kcId/gruppen to create, GET participant-candidates, and POST/DELETE /chat/gruppen/:channelId/participants to manage membership (creator, LT, or Verantwortliche/r of that KC) - ChatGateway broadcasts chat:participants-changed on membership change - PushService updated for nullable ChatParticipant.userId + new guestAccountId column - SyncService now replicates ChatParticipant - Prisma migration + 14 new unit tests (75/75 passing), tsc clean - CI: add .gitea/workflows/cybedefend-scan.yml + .cybedefend project config