Show monthly usage when AI credits are unlimited

Currently when admins do not set any limit for AI credits, usage in status line shows **Monthly: no limit**.

It would be nice if showed the total usage for current month so one has a way to estimate their spending and act accordingly.

Start by locating the CLI status-line code that renders the monthly AI-credit limit and the code that obtains usage totals. Update the unlimited-credit case to show current-month usage while retaining the unlimited status, then verify the status line reports the total and remains correct when no limit is configured.

Written by the indexing model from the issue text.