- Added `useTeamMessagesRead` hook to manage read state of messages within a team, utilizing local storage for persistence.
- Introduced `toMessageKey` utility for generating stable keys for messages based on their properties.
- Enhanced `CollapsibleTeamSection` to display a secondary badge for unread message counts.
- Updated `TeamDetailView` to calculate and pass unread message counts to `CollapsibleTeamSection`.
- Implemented message visibility tracking in `ActivityTimeline` to mark messages as read when they enter the viewport.
