Allow User to Rerun Setup Wizard

User in 4862634-zen asked to rerun setup wizard, which isn't currently possible.

Suggest: create ability to rerun wizard, as described in this [Sensei post](https://senseilms.com/celebrating-wins-with-the-course-completed-page/).

Start by locating the plugin's setup wizard entry point and read the linked Sensei post for the intended behavior. Define the rerun flow and its completion criteria before implementing it, then verify that an existing user can launch and complete the wizard again without disrupting current setup.

Written by the indexing model from the issue text.