Private roadmap-only items selectable in roadmap tasks

Description: As a product manager, I want to create and manage roadmap-only items that remain hidden from the feedback board while still being selectable within roadmap tasks, so that we can maintain internal initiatives without exposing them publicly. Problem: Currently, adding an item to the roadmap automatically surfaces it on the feedback board. If the feedback board association is removed, the item/category can no longer be selected for roadmap tasks. This prevents us from maintaining an internal-only roadmap while preserving task linkage and workflow integrity. Benefit: Maintain an internal roadmap that does not appear on public/user-facing feedback boards. Keep items selectable in roadmap task pickers, dependencies, and workflows. Reduce feedback board noise and protect sensitive initiatives without workarounds.