Sticky thead was floating mid-content when the container auto-scrolled
as new log entries arrived. Pinning scrollTop to 0 on each logs update
keeps the thead at position 0 where it belongs.
- Use height: 480px on .dash-grid so both columns are the same height;
side panels split that height via flex instead of their own max-height
- Add LayoutDashboard icon to the DASHBOARD page header
