[Bug] Completed statuses configured for the backlog are still hidden #481

When a completed status such as Done is selected under Configure Board → Backlog, items with that status do not appear in the backlog.

The backlog client implicitly adds status_completed = false. This overrides the configured backlog statuses.

Expected behavior

Statuses explicitly configured for the backlog should be shown, including completed statuses.

Actual behavior

Items with a completed status remain hidden.

A fix is proposed in #395.