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/update.go

@@ -11,6 +11,7 @@ import (
 const (
 	imageName           = "hub.davinti.com.br:443/app-dono/app-cliente:latest"
 	wireguardImageName  = "hub.davinti.com.br:443/davinti-vproxy:latest"
+	updaterImageName    = "docker:cli"
 	configPath          = "config.toml"
 	wireguardConfigPath = "envs"
 )
@@ -138,6 +139,8 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		return m.updateGenerateFile(msg)
 	case StepRunDocker:
 		return m.updateRunDocker(msg)
+	case StepRunUpdater:
+		return m.updateRunUpdater(msg)
 	case StepDone:
 		return m, tea.Quit
 	}
@@ -396,6 +399,49 @@ func (m Model) updateRunDocker(msg tea.Msg) (tea.Model, tea.Cmd) {
 			default:
 				return m, tea.Quit
 			}
+		} else if m.finishedDockerRun && m.dockerRunError == nil {
+			m.currentStep = StepRunUpdater
+
+			m.finishedDockerRun = false
+			m.dockerRunError = nil
+
+			return m, RunUpdaterContainer(
+				imageName,
+				"app-dono-cliente",
+				configPath,
+				fmt.Sprintf("/app/%s", configPath),
+				m.configValues,
+			)
+		}
+	}
+
+	return m, nil
+}
+
+// updateRunUpdater starts the auto-update agent that watches the app-dono-cliente
+// container and pulls/recreates it whenever a new image is pushed to :latest.
+func (m Model) updateRunUpdater(msg tea.Msg) (tea.Model, tea.Cmd) {
+	switch msg := msg.(type) {
+	case DockerRunMsg:
+		m.finishedDockerRun = true
+		m.dockerRunError = msg.Err
+
+	case tea.KeyPressMsg:
+		if m.finishedDockerRun && m.dockerRunError != nil {
+			switch msg.String() {
+			case "r":
+				m.finishedDockerRun = false
+				m.dockerRunError = nil
+				return m, RunUpdaterContainer(
+					imageName,
+					"app-dono-cliente",
+					configPath,
+					fmt.Sprintf("/app/%s", configPath),
+					m.configValues,
+				)
+			default:
+				return m, tea.Quit
+			}
 		} else if m.finishedDockerRun && m.dockerRunError == nil {
 			m.currentStep = StepDone
 		}