fix(tui): track selection by site ID + q means back everywhere

Cursor tracked by site ID instead of positional index. When the
list re-sorts every tick (sites change status), the selection stays
on the same monitor instead of silently jumping to whatever now
occupies that index position.

q now means "back" in detail, history, SLA, and alert-detail views
— consistent with muscle memory from navigating deeper views.
Only the dashboard q quits the app. ctrl+c always quits from
anywhere.

internal/tui/data.go

@@ -105,9 +105,24 @@ func (m *Model) refreshLive() {
 	}
 	m.sites = ordered
 	m.logViewport.SetContent(strings.Join(m.engine.GetLogs(), "\n"))
+
+	if m.currentTab == 0 && m.selectedID != 0 {
+		for i, s := range m.sites {
+			if s.ID == m.selectedID {
+				m.cursor = i
+				break
+			}
+		}
+	}
 	m.clampCursor()
 }
 
+func (m *Model) syncSelectedID() {
+	if m.currentTab == 0 && m.cursor < len(m.sites) {
+		m.selectedID = m.sites[m.cursor].ID
+	}
+}
+
 // clampCursor keeps the cursor and scroll offset within the current tab's list.
 func (m *Model) clampCursor() {
 	listLen := m.currentListLen()