Login Loop

README.md

@@ -34,6 +34,11 @@ administrator. That account can sign in at `/manager/sign-in`, create
 businesses, edit their primary domains, and share the one-time owner setup
 link generated during provisioning.
 
+For an existing installation created before this platform/tenant split, the
+recorded `initialAdminUserId` account is allowed to sign in once and is
+promoted to the platform administrator. No other business owner can use that
+upgrade path.
+
 Business provisioning creates the tenant domain, settings, booking rules,
 opening hours, system roles, owner staff profile, and seven-day owner
 invitation in one transaction. The owner chooses a password through that