feat(tui): mouse click for settings sections, column sort, logs toggle

- Click Alerts/Nodes/Users sub-tabs in settings to switch sections
- Click STATUS/NAME/LATENCY column headers to sort (click again
  to reverse direction)
- Click logs panel to toggle focus (click again to unfocus)

internal/tui/update.go

@@ -840,11 +840,49 @@ func (m *Model) handleClick(msg tea.MouseMsg) (tea.Model, tea.Cmd) {
 		}
 	}
 
+	if m.currentTab == tabSettings {
+		maxSec := 1
+		if m.isAdmin {
+			maxSec = 2
+		}
+		for i := 0; i <= maxSec; i++ {
+			if m.zones.Get(fmt.Sprintf("section-%d", i)).InBounds(msg) {
+				m.switchSettingsSection(i)
+				return m, nil
+			}
+		}
+	}
+
 	if m.currentTab == tabMonitors {
+		sortZones := []struct {
+			zone string
+			col  int
+		}{
+			{"sort-status", sortStatus},
+			{"sort-name", sortName},
+			{"sort-latency", sortLatency},
+		}
+		for _, sz := range sortZones {
+			if m.zones.Get(sz.zone).InBounds(msg) {
+				if m.sortColumn == sz.col {
+					m.sortAsc = !m.sortAsc
+				} else {
+					m.sortColumn = sz.col
+					m.sortAsc = false
+				}
+				m.refreshLive()
+				return m, nil
+			}
+		}
+
 		if m.zones.Get("panel-monitors").InBounds(msg) {
 			m.focusedPanel = panelMonitors
 		} else if m.zones.Get("panel-logs").InBounds(msg) {
-			m.focusedPanel = panelLogs
+			if m.focusedPanel == panelLogs {
+				m.focusedPanel = panelMonitors
+			} else {
+				m.focusedPanel = panelLogs
+			}
 			return m, nil
 		} else if m.detailOpen && m.zones.Get("panel-detail").InBounds(msg) {
 			m.focusedPanel = panelDetail