Add optional CTA button to in-app announcement popups in new editor

Description: Reintroduce an optional Call-To-Action (CTA) button component in the new in-app announcement popup editor. This component should be opt-in and allow users to add and edit a CTA for announcements with the same capabilities they had prior to the Admin panel redesign. Problem: The new editor removed CTA buttons from in-app announcement popups by design. Teams previously relied on a CTA to drive user actions and need to configure and edit the CTA before launching new announcements. Without this option, announcements may be delayed or lose effectiveness. Benefit: Restoring an optional, editable CTA preserves established workflows, maintains engagement and conversion from announcements, and enables teams to publish on schedule while keeping the new editor streamlined for those who don’t need a CTA.