registerApp minted a client_secret whose hash nothing ever verified (six
routes gate on the shared-secret caller-identity check, not on registration);
registered_apps sits empty on the live host. Deleted: POST /v1/apps,
getRegistrationSecret, config.appRegistrationSecret, registerApp/
hashClientSecret/verifyClientSecret, the client_secret_hash column (dropped
idempotently on startup, same as it is created), and
tests/app-registration-endpoint.test.ts. registered_apps and resolveAppProfile
stay as a profile store; app-registry.test.ts fixtures that used registerApp
purely to seed a profile now write through store.registerApp directly, the
same primitive the built-in-shadow test already used.
776565effd