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/docker_test.go

@@ -0,0 +1,41 @@
+package tui
+
+import (
+	"os/exec"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// TestShellQuoteArgsRoundTrip guards the updater's poll-script generation: cv fields
+// (e.g. cert_dir_path) are operator-entered and get embedded into a shell script run
+// inside the updater container. If shellQuote/shellQuoteArgs mis-escapes a value, that's
+// a command-injection bug, not just a cosmetic one. This feeds tricky values through a
+// real `sh` and checks they come back out exactly as they went in.
+func TestShellQuoteArgsRoundTrip(t *testing.T) {
+	if _, err := exec.LookPath("sh"); err != nil {
+		t.Skip("sh not available")
+	}
+
+	cases := [][]string{
+		{"simple"},
+		{"has space"},
+		{"it's got a quote"},
+		{"$(echo injected)"},
+		{"a;b|c&d"},
+		{"back`tick`"},
+		{"multi", "arg space", "o'clock", "$HOME", "'"},
+	}
+
+	for _, args := range cases {
+		script := "printf '%s\\n' " + shellQuoteArgs(args)
+		out, err := exec.Command("sh", "-c", script).Output()
+		if err != nil {
+			t.Fatalf("sh failed for %v: %v", args, err)
+		}
+		got := strings.Split(strings.TrimRight(string(out), "\n"), "\n")
+		if !reflect.DeepEqual(got, args) {
+			t.Errorf("round trip mismatch for %v: got %v", args, got)
+		}
+	}
+}