fix: 500 on setup complete + wizard shows all 7 steps

Two bugs:

1. AttributeError: AuthManager.update_password does not exist — the
   fallback when create_user fails should call set_password_admin().
   This caused a 500 on every setup submit when an admin user already
   existed (e.g. from a previous install attempt).

2. Wizard was jumping to step 2 and skipping domain steps 3-4 when
   preconfigured data existed in cell_config.json. Since the installer
   no longer sets that data, and the wizard must always show all steps,
   the installerConfigured state and all step-skipping navigation is
   removed. Values are still pre-filled if found in config.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/setup_manager.py

@@ -223,7 +223,7 @@ class SetupManager:
                 role='admin',
             )
             if not ok:
-                ok = self.auth_manager.update_password('admin', password)
+                ok = self.auth_manager.set_password_admin('admin', password)
             if not ok:
                 return {'success': False, 'errors': ['Failed to set admin password.']}