fix(tui): remove extra blank lines above footer

JoinVertical adds no gap lines between sections. The - 2
subtraction was over-reserving space, leaving 2 blank lines
between content and footer.

internal/tui/view_dashboard.go

@@ -181,7 +181,7 @@ func (m Model) viewDashboard() string {
 		availHeight = 5
 	}
 
-	contentHeight := availHeight - lipgloss.Height(header) - lipgloss.Height(footer) - 2
+	contentHeight := availHeight - lipgloss.Height(header) - lipgloss.Height(footer)
 	if contentHeight < 1 {
 		contentHeight = 1
 	}