Delete Monitored Topic

Permanently deletes a Monitored Topic. Cascade: (1) any Topic campaign bound to this topic loses the binding — the binding is soft-hidden and the campaign’s keyword set is regenerated automatically; (2) Prospects campaigns that use this topic in postActivityFilter.monitoredTopicIds are NOT auto-cleaned — the id stays in the filter array but will no longer match anything, and the campaign must be updated if the filter should reflect the change.