Authenticate with Akarso via browser-based device flow.

Prints a verification URL and a short code, then opens the browser for the user to approve. Once approved, an API key is created and saved automatically. Run akarso auth check afterwards to confirm the login succeeded and see which profile the key targets.

This command must stay alive while the user approves in the browser. It returns on its own once approval completes or the code expires (default: 5 minutes).