Prevent and clean up empty Runbooks attached to maps

NetBrain currently allows empty Runbooks, containing no nodes beyond the Start node, to be saved and remain attached to maps, with no mechanism to identify or remove them in bulk. This enhancement would introduce a way to detect and bulk-delete existing empty Runbooks across maps, along with a safeguard that prevents new empty Runbooks from being saved with a map going forward. Customers who rely on frequently accessed maps for critical sites would benefit from a cleaner Runbook list, reducing time spent opening multiple Runbooks to identify the correct one to execute.