fix: localize native tray menu

internal/core/appsettings/manager.go

@@ -78,9 +78,10 @@ type WindowState struct {
 
 // Manager provides thread-safe access to app settings.
 type Manager struct {
-	mu         sync.RWMutex
-	config     *Config
-	configPath string
+	mu                sync.RWMutex
+	config            *Config
+	configPath        string
+	onLanguageChanged func(string)
 }
 
 // DefaultConfigPath returns the default path for app settings.
@@ -230,13 +231,32 @@ func (m *Manager) UpdateLanguage(language string) error {
 	}
 
 	m.mu.Lock()
-	defer m.mu.Unlock()
 	if m.config == nil {
 		m.config = defaultConfig()
 	}
 	m.config.Language = language
 	m.config.LastOpenedAt = time.Now().UTC().Format(time.RFC3339)
-	return m.saveLocked()
+	err := m.saveLocked()
+	handler := m.onLanguageChanged
+	m.mu.Unlock()
+	if err != nil {
+		return err
+	}
+	if handler != nil {
+		handler(language)
+	}
+	return nil
+}
+
+// SetLanguageChangedHandler registers the shell callback invoked after a
+// language preference has been durably updated.
+func (m *Manager) SetLanguageChangedHandler(handler func(string)) {
+	if m == nil {
+		return
+	}
+	m.mu.Lock()
+	m.onLanguageChanged = handler
+	m.mu.Unlock()
 }
 
 // UpdateSync replaces sync settings without changing unrelated app settings.

internal/core/appsettings/manager_test.go

@@ -3,6 +3,7 @@ package appsettings
 import (
 	"os"
 	"path/filepath"
+	"reflect"
 	"testing"
 )
 
@@ -74,6 +75,34 @@ func TestUpdateLanguagePersistsAndPreservesUnrelatedSettings(t *testing.T) {
 	}
 }
 
+func TestUpdateLanguageNotifiesTheDesktopShellAfterPersisting(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "config.json")
+	manager := NewManager(path)
+	if err := manager.Load(); err != nil {
+		t.Fatal(err)
+	}
+
+	var received []string
+	manager.SetLanguageChangedHandler(func(language string) {
+		received = append(received, language)
+	})
+	if err := manager.UpdateLanguage(LanguageRussian); err != nil {
+		t.Fatalf("UpdateLanguage: %v", err)
+	}
+	if got := manager.Get().Language; got != LanguageRussian {
+		t.Fatalf("persisted language = %q, want %q", got, LanguageRussian)
+	}
+	if !reflect.DeepEqual(received, []string{LanguageRussian}) {
+		t.Fatalf("language notifications = %#v, want [%q]", received, LanguageRussian)
+	}
+	if err := manager.UpdateLanguage("de"); err == nil {
+		t.Fatal("UpdateLanguage(de) succeeded, want validation failure")
+	}
+	if !reflect.DeepEqual(received, []string{LanguageRussian}) {
+		t.Fatalf("language notification fired after rejected update: %#v", received)
+	}
+}
+
 func TestLoad_CorruptConfig(t *testing.T) {
 	dir := t.TempDir()
 	path := filepath.Join(dir, "config.json")