User lookups no longer trip over the User type definition

On long-lived installations, the built-in "User" type definition had once been saved to the database claiming to be a user itself. Every user lookup then received that definition row alongside real accounts, which degraded identity resolution (display name, time zone, language) and produced a steady stream of background errors. The platform now detects and corrects such rows automatically at startup, so the user directory returns only real accounts.