Added 15 test cases covering: - Create, GetByID, GetByDeviceID - Update, Delete - List, ListByUserID, ListByStatus - UpdateStatus, Exists - DeleteByUserID, DeleteAllByUserIDExcept - GetActiveDevices, TrustDevice, UntrustDevice - GetTrustedDevices, ListAll Coverage: 46.6% -> 49.0% (+2.4%) Addresses P1: repository layer test coverage