android: splash screen with background color on Android 12+ (#3579)

apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/platform/Platform.kt

@@ -10,6 +10,7 @@ interface PlatformInterface {
   fun androidChatStopped() {}
   fun androidChatInitializedAndStarted() {}
   fun androidIsBackgroundCallAllowed(): Boolean = true
+  fun androidSetNightModeIfSupported() {}
   suspend fun androidAskToAllowBackgroundCalls(): Boolean = true
 }
 /**

apps/multiplatform/common/src/commonMain/kotlin/chat/simplex/common/ui/theme/ThemeManager.kt

@@ -7,6 +7,7 @@ import androidx.compose.ui.text.font.FontFamily
 import chat.simplex.res.MR
 import chat.simplex.common.model.AppPreferences
 import chat.simplex.common.model.ChatController
+import chat.simplex.common.platform.platform
 import chat.simplex.common.views.helpers.generalGetString
 
 // https://github.com/rsms/inter
@@ -96,6 +97,7 @@ object ThemeManager {
   fun applyTheme(theme: String, darkForSystemTheme: Boolean) {
     appPrefs.currentTheme.set(theme)
     CurrentColors.value = currentColors(darkForSystemTheme)
+    platform.androidSetNightModeIfSupported()
   }
 
   fun changeDarkTheme(theme: String, darkForSystemTheme: Boolean) {