feat: auto-update app-dono-cliente when a new image is pushed to :latest

Adds a StepRunUpdater step that starts app-dono-updater after the app
container comes up: a poll loop (docker pull, compare image IDs,
recreate on change) baked into the official docker:cli image via
`sh -c`, reusing the same docker run argv as the initial container
start so the two can't drift.

Not built on Watchtower: containrrr/watchtower was archived upstream
in Dec 2025 with no maintained successor recommended for production
use, so this avoids taking on that dependency.

internal/tui/view.go

@@ -107,6 +107,11 @@ func (m Model) View() tea.View {
 		if m.finishedDockerRun && m.dockerRunError != nil {
 			helpMsg = retryMsg
 		}
+	case StepRunUpdater:
+		body = m.viewDockerRun()
+		if m.finishedDockerRun && m.dockerRunError != nil {
+			helpMsg = retryMsg
+		}
 	case StepDone:
 		body = m.viewDoneMessage()
 		helpMsg = anyKeyOutMsg