Fix: 真正修复双启动页 - 移除 windowBackground 覆盖，让系统启动窗口独占

之前同时设置 windowBackground 和 windowSplashScreenAnimatedIcon 导致两个画面都显示 appstore.png，仍可见两个启动页。现在 SplashTheme 不再覆盖 windowBackground，仅由系统启动窗口显示 appstore.png，Activity 启动后直接进入主界面。

Android-kotlin-Code/app/src/main/res/values-night/themes.xml

@@ -2,7 +2,5 @@
 <resources>
     <style name="BootstrapTheme" parent="AppThemeDark" />
 
-    <style name="SplashTheme" parent="BootstrapTheme">
-        <item name="android:windowBackground">@drawable/splash_background</item>
-    </style>
+    <style name="SplashTheme" parent="BootstrapTheme" />
 </resources>

Android-kotlin-Code/app/src/main/res/values-v31/themes.xml

@@ -1,7 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <style name="SplashTheme" parent="BootstrapTheme">
-        <item name="android:windowBackground">@drawable/splash_background</item>
         <item name="android:windowSplashScreenBackground">@color/white</item>
         <item name="android:windowSplashScreenAnimatedIcon">@drawable/appstore</item>
         <item name="android:windowSplashScreenIconBackgroundColor">@color/white</item>

Android-kotlin-Code/app/src/main/res/values/themes.xml

@@ -2,7 +2,5 @@
 <resources>
     <style name="BootstrapTheme" parent="AppThemeLight" />
 
-    <style name="SplashTheme" parent="BootstrapTheme">
-        <item name="android:windowBackground">@drawable/splash_background</item>
-    </style>
+    <style name="SplashTheme" parent="BootstrapTheme" />
 </resources>