feat: Implement navigation bar visibility handling based on navigation mode

app/src/main/java/com/rosetta/messenger/ui/theme/Theme.kt

@@ -13,6 +13,7 @@ import androidx.compose.ui.graphics.toArgb
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.platform.LocalView
 import androidx.core.view.WindowCompat
+import com.rosetta.messenger.ui.utils.NavigationModeUtils
 import kotlinx.coroutines.delay
 
 private val DarkColorScheme = darkColorScheme(
@@ -63,14 +64,17 @@ fun RosettaAndroidTheme(
         else -> LightColorScheme
     }
     val view = LocalView.current
+    val context = LocalContext.current
     if (!view.isInEditMode) {
         SideEffect {
             val window = (view.context as android.app.Activity).window
+            val insetsController = WindowCompat.getInsetsController(window, view)
             // Make status bar transparent for wave animation overlay
             window.statusBarColor = AndroidColor.TRANSPARENT
-            // Navigation bar color is managed by OnboardingScreen for smooth transition
-            // Don't change it here to avoid instant color change
-            WindowCompat.getInsetsController(window, view).isAppearanceLightStatusBars = !darkTheme
+            insetsController.isAppearanceLightStatusBars = !darkTheme
+
+            // Navigation bar: показываем только если есть нативные кнопки
+            NavigationModeUtils.applyNavigationBarVisibility(insetsController, context, darkTheme)
         }
     }