Stagger setTimeout calls inside the for loop were never cleared on
component unmount, causing potential setState calls on unmounted
components when the user navigates away before all toasts fire.
Fixes#1094
- Replaced the existing announcement card and empty state components with imports from the new announcements directory.
- Introduced state management for the announcements sidebar in the LayoutDataProvider.
- Updated navigation items to handle announcements sidebar toggling.
- Integrated AnnouncementsSidebar into the LayoutShell for both mobile and desktop views.
- Enhanced sidebar handling to improve user experience when navigating announcements.
- Added startTime and endTime properties to announcements for time-bound visibility.
- Introduced audience targeting to control who sees announcements (all, users, web_visitors).
- Updated related components and hooks to support new announcement features.
- Removed unused state tracking for dismissed announcements to streamline functionality.
