Simulator does not work with default credentials

This is a side effect of #1385 (closed). When a user sets the password after the first login, the simulator doesn't work because it relies on default admin/admin credentials:

ERRO[2024-10-30 11:57:18]            users.go:181   User not found, cannot authenticate           identifier="admin" method="internal"
INFO[2024-10-30 11:57:18]       middleware.go:106   HTTP request served                           method="POST" path="/api/sessions" remote="127.0.0.1:54856" size="0" status="400" text_status="Bad Request" took="24.680625ms"