fix: propagate context cancellation during license pre-flight

The offline-degradation branch in validateLicense treated any non-LicenseError
as an unreachable server. A cancelled caller context (Ctrl+C) also surfaces
there, so it was swallowed — printing a misleading "Could not reach the license
server" warning and letting the start continue. Propagate ctx.Err() before
degrading; the client's own request timeout is distinct from ctx and still
falls through to the offline fallback.

Generated with [Linear](https://linear.app/localstack/issue/DEVX-703/support-enterprise-environments-that-cannot-pull-from-docker-hub#agent-session-77e3f9fc)

Co-authored-by: linear-code[bot] <222613912+linear-code[bot]@users.noreply.github.com>

Author: gtsiolis

internal/container/start.go

@@ -605,6 +605,12 @@ func validateLicense(ctx context.Context, sink output.Sink, opts StartOptions, c
 	licenseResp, err := opts.PlatformClient.GetLicense(ctx, licenseReq)
 	if err != nil {
 		sink.Emit(output.SpinnerStop())
+		// A cancelled caller context (e.g. Ctrl+C) is not an offline condition —
+		// propagate it instead of degrading. The client's own request timeout is
+		// distinct from ctx and still falls through to the offline fallback below.
+		if ctx.Err() != nil {
+			return ctx.Err()
+		}
 		var licErr *api.LicenseError
 		if !errors.As(err, &licErr) {
 			// The license server responded with no definitive verdict — the request

internal/container/start_test.go

@@ -492,6 +492,34 @@ func TestValidateLicense_FailsOnServerRejection(t *testing.T) {
 	assert.Contains(t, err.Error(), "license validation failed")
 }
 
+func TestValidateLicense_PropagatesContextCancellation(t *testing.T) {
+	// A cancelled caller context (Ctrl+C) must surface as cancellation, not be
+	// mistaken for an offline license server.
+	opts := StartOptions{
+		PlatformClient: api.NewPlatformClient("http://127.0.0.1:1", log.Nop()),
+		Logger:         log.Nop(),
+		Telemetry:      telemetry.New("", true),
+	}
+	c := runtime.ContainerConfig{
+		EmulatorType: config.EmulatorAWS,
+		ProductName:  "localstack-pro",
+		Tag:          "2026.4",
+		Image:        "localstack/localstack-pro:2026.4",
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	var out bytes.Buffer
+	sink := output.NewPlainSink(&out)
+
+	err := validateLicense(ctx, sink, opts, c, "tok", filepath.Join(t.TempDir(), "license.json"))
+
+	require.ErrorIs(t, err, context.Canceled)
+	assert.NotContains(t, out.String(), "Could not reach the license server",
+		"a cancellation must not be reported as an unreachable license server")
+}
+
 func TestStartContainers_SnowflakeLicenseError(t *testing.T) {
 	ctrl := gomock.NewController(t)
 	mockRT := runtime.NewMockRuntime(ctrl)