fix(tui): add ANSI-16 color fallbacks for SSH terminals

Theme colors now use lipgloss.CompleteColor with hand-picked ANSI-16
values instead of raw hex. Prevents algorithmic degradation from
collapsing dark backgrounds into indistinguishable ANSI colors over
SSH. Backgrounds fall through to terminal default in 16-color mode;
semantic colors map to distinct ANSI indices (green/yellow/red/blue/
cyan/magenta). TrueColor rendering is unchanged.

internal/tui/tab_sites.go

@@ -204,7 +204,7 @@ func (m Model) viewSitesTab() string {
 			for i := start; i < end; i++ {
 				site := m.sites[i]
 				rowIdx := i - start
-				var rowBg lipgloss.Color
+				var rowBg lipgloss.TerminalColor
 				if i == m.cursor {
 					rowBg = m.theme.SelectedBg
 				} else if rowIdx%2 == 1 {