[client] Enable launch-on-login by default on fresh GUI installs (#6738)

* [client] Add autostart preference marker and MDM disableAutostart key

Adds the autostartInitialized marker to the Wails UI preferences store so
the one-time autostart default decision can persist per OS user, and a
UI-only disableAutostart MDM policy key that suppresses the default and
flows into GetConfigResponse.mDMManagedFields like disableAutoConnect.

* [client] Enable launch-on-login by default on fresh GUI installs

On the first interactive run the GUI persists the autostartInitialized
marker before any enable attempt, then enables autostart only when the
platform supports it, MDM policy does not disable it, the process was not
relaunched by an installer/updater (--post-update), and the installer's
fresh-install breadcrumb is present. Upgrading users have no breadcrumb,
so an update can never write login items, and a user's disable in
Settings is never overridden.

* [release] Write fresh-install breadcrumb from installers

Installers write a .fresh-install breadcrumb on fresh installs only and
delete stale breadcrumbs on upgrade; none of them writes login items or
registry Run keys. Windows NSIS detects upgrades via the uninstall
registry entry or an existing installed executable; the macOS pkg via the
previous pkgutil receipt; Linux deb/rpm via the standard postinstall
arguments. Post-update GUI relaunches (macOS open, Linux
ui-post-install.sh) pass --post-update so the first-run autostart default
cannot fire on updates.

* Revert installer breadcrumb changes

The real Windows installer does uninstall-then-install and deletes
$INSTDIR, so a breadcrumb written there cannot survive or discriminate
a fresh install from an upgrade. Restore the three installer files to
their main versions; no installer or updater writes an autostart entry.

* Detect fresh install from NetBird footprint instead of installer breadcrumb

Replace the installer-written breadcrumb discriminator with a GUI-side
check. netbirdFootprintExists inspects the daemon config/state files
(default.json, legacy config.json, state.json) under profilemanager's
default config dir; combined with whether the UI preferences file already
existed, this tells a genuinely fresh machine from an existing or
upgrading user. Only the signed GUI, via Wails, ever enables
launch-on-login, and a user's later manual disable is never overridden.
The preferences store now exposes ExistedAtLoad and the --post-update
flag is dropped.

* Update tests for footprint-based autostart default

Table tests for shouldEnableAutostartDefault now cover supported,
mdmDisabled, and priorInstall guards plus precedence; breadcrumb and
post-update cases are removed. Add a store test asserting ExistedAtLoad
is false with no file and true after persisting and reopening.

client/ui/preferences/store.go

@@ -54,6 +54,10 @@ type UIPreferences struct {
 	Language            i18n.LanguageCode `json:"language"`
 	ViewMode            ViewMode          `json:"viewMode"`
 	OnboardingCompleted bool              `json:"onboardingCompleted"`
+	// AutostartInitialized records that the one-time autostart default
+	// decision has run for this OS user. It only ever transitions to true
+	// and is never reset, so the default-on flow runs at most once, ever.
+	AutostartInitialized bool `json:"autostartInitialized"`
 }
 
 // LanguageValidator rejects SetLanguage inputs with no shipped bundle.
@@ -72,8 +76,9 @@ type Emitter interface {
 type Store struct {
 	path string
 
-	mu      sync.RWMutex
-	current UIPreferences
+	mu            sync.RWMutex
+	current       UIPreferences
+	existedAtLoad bool
 
 	subsMu sync.Mutex
 	subs   []chan UIPreferences
@@ -157,6 +162,27 @@ func (s *Store) SetOnboardingCompleted(done bool) error {
 	return nil
 }
 
+// SetAutostartInitialized persists the one-time autostart decision marker.
+// No-op if unchanged.
+func (s *Store) SetAutostartInitialized(done bool) error {
+	s.mu.Lock()
+	if s.current.AutostartInitialized == done {
+		s.mu.Unlock()
+		return nil
+	}
+	next := s.current
+	next.AutostartInitialized = done
+	if err := s.persistLocked(next); err != nil {
+		s.mu.Unlock()
+		return fmt.Errorf("persist preferences: %w", err)
+	}
+	s.current = next
+	s.mu.Unlock()
+
+	s.broadcast(next)
+	return nil
+}
+
 // SetLanguage validates, persists, and broadcasts. No-op if unchanged.
 func (s *Store) SetLanguage(lang i18n.LanguageCode) error {
 	if lang == "" {
@@ -206,13 +232,29 @@ func (s *Store) Subscribe() (<-chan UIPreferences, func()) {
 	return ch, unsubscribe
 }
 
+// ExistedAtLoad reports whether the backing preferences file was present on
+// disk when the store loaded. It distinguishes a user who ran a prior GUI
+// version from a brand-new OS user with no preferences yet.
+func (s *Store) ExistedAtLoad() bool {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return s.existedAtLoad
+}
+
 // load reads the file into current. A missing file is not an error (the
 // in-memory default stands); malformed contents return an error.
 func (s *Store) load() error {
-	if _, err := os.Stat(s.path); errors.Is(err, os.ErrNotExist) {
-		return nil
+	if _, err := os.Stat(s.path); err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil
+		}
+		return fmt.Errorf("stat preferences: %w", err)
 	}
 
+	s.mu.Lock()
+	s.existedAtLoad = true
+	s.mu.Unlock()
+
 	var loaded UIPreferences
 	if _, err := util.ReadJson(s.path, &loaded); err != nil {
 		return err

client/ui/preferences/store_test.go

@@ -215,6 +215,46 @@ func TestStore_FileShapeIsJSON(t *testing.T) {
 	assert.Equal(t, i18n.LanguageCode("hu"), parsed.Language)
 }
 
+func TestStore_SetAutostartInitializedPersistsAcrossReload(t *testing.T) {
+	withTempConfigDir(t)
+	emitter := &recordingEmitter{}
+	s, err := NewStore(nil, emitter)
+	require.NoError(t, err)
+
+	assert.False(t, s.Get().AutostartInitialized, "marker must default to false when no file is on disk")
+
+	require.NoError(t, s.SetAutostartInitialized(true))
+	assert.True(t, s.Get().AutostartInitialized, "Get should reflect the persisted marker")
+	require.Len(t, emitter.calledWith(EventPreferencesChanged), 1, "first marker write should broadcast")
+
+	// Re-setting the same value must be a no-op: no disk write, no broadcast.
+	require.NoError(t, s.SetAutostartInitialized(true))
+	assert.Len(t, emitter.calledWith(EventPreferencesChanged), 1, "idempotent marker write should not broadcast again")
+
+	// A fresh Store (new GUI launch) must see the marker so the autostart
+	// default decision never runs twice.
+	reloaded, err := NewStore(nil, nil)
+	require.NoError(t, err)
+	assert.True(t, reloaded.Get().AutostartInitialized, "marker must survive a reload from disk")
+}
+
+func TestStore_ExistedAtLoad(t *testing.T) {
+	withTempConfigDir(t)
+
+	// Brand-new OS user: no preferences file on disk yet.
+	fresh, err := NewStore(nil, nil)
+	require.NoError(t, err)
+	assert.False(t, fresh.ExistedAtLoad(), "ExistedAtLoad must be false when no file is on disk")
+
+	// Persisting a value writes the file to disk.
+	require.NoError(t, fresh.SetLanguage("en"))
+
+	// A subsequent GUI launch reopens the now-present file.
+	reopened, err := NewStore(nil, nil)
+	require.NoError(t, err)
+	assert.True(t, reopened.ExistedAtLoad(), "ExistedAtLoad must be true after the store has persisted and is reopened")
+}
+
 func TestStore_ErrUnsupportedSentinel(t *testing.T) {
 	// Verifies callers can match on the sentinel error rather than parsing
 	// strings — protects against accidental %v -> %w changes that would