fix(tui): enforce column MaxWidth to prevent lipgloss redistribution

lipgloss table with Width(tableWidth) redistributes surplus space across
all columns. Adding MaxWidth() caps each column to its computed width.
Also dump any remaining surplus into the HISTORY sparkline column.

internal/tui/tab_sites.go

@@ -439,6 +439,10 @@ func (m Model) computeLayout() tableLayout {
 		widths[i] = w
 	}
 
+	if surplus > 0 {
+		widths[6] += surplus
+	}
+
 	return tableLayout{
 		nameW:     nameW,
 		sparkW:    sparkW,