- Added new attributes for chat colors including rail, date rules, and unread markers.
- Enhanced ChatLine class to support colored segments for continuation lines and horizontal separator rules.
- Introduced a WelcomeBanner class to display a splash screen when no channel is selected.
- Implemented NickColorHelper for deterministic per-nick colors, ensuring consistent user color representation.
- Updated ChannelListSource to highlight channels with unread messages and mentions.
- Improved MainWindow to include a spinner for transitional connection states and display activity in the status bar.
- Added unit tests for NickColorHelper to ensure stable and predictable color indexing.
