fix: 修复PR #1448合并后ReadConfig.readMenuBlurAlpha编译错误

PR #1448错误引用了ReadConfig.readMenuBlurAlpha（不存在），
ReadConfig上正确的属性名是menuAlpha，统一修正引用。

app/src/main/java/io/legado/app/help/config/AppConfig.kt

@@ -125,7 +125,7 @@ object AppConfig : SharedPreferences.OnSharedPreferenceChangeListener {
         ReadConfig.pageTouchSlop = preferences.pageTouchSlop
         ReadConfig.showReadTitleAddition = preferences.showReadTitleAddition
         ReadConfig.titleBarMode = preferences.titleBarMode
-        ReadConfig.readMenuBlurAlpha = preferences.readMenuBlurAlpha
+        ReadConfig.menuAlpha = preferences.menuAlpha
         ReadConfig.readSliderMode = preferences.readSliderMode
         readBarStyleFollowPageValue = preferences.readBarStyleFollowPage
         readBarStyleValue = preferences.readBarStyle
@@ -837,9 +837,9 @@ object AppConfig : SharedPreferences.OnSharedPreferenceChangeListener {
             ThemeConfig.enableBlur = value
         }
     var menuAlpha: Int
-        get() = ReadConfig.readMenuBlurAlpha
+        get() = ReadConfig.menuAlpha
         set(value) {
-            ReadConfig.readMenuBlurAlpha = value
+            ReadConfig.menuAlpha = value
         }
 
     var readSliderMode

app/src/main/java/io/legado/app/ui/config/readConfig/ReadConfig.kt

@@ -130,7 +130,7 @@ object ReadConfig {
         expandTextMenu = preferences.expandTextMenu
         showReadTitleAddition = preferences.showReadTitleAddition
         titleBarMode = preferences.titleBarMode
-        readMenuBlurAlpha = preferences.readMenuBlurAlpha
+        menuAlpha = preferences.menuAlpha
         readSliderMode = preferences.readSliderMode
         readBarStyleFollowPage = preferences.readBarStyleFollowPage
         readBarStyle = preferences.readBarStyle

app/src/main/java/io/legado/app/ui/config/readConfig/ReadConfigViewModel.kt

@@ -60,8 +60,8 @@ class ReadConfigViewModel(
                 }
 
                 is ReadConfigIntent.ReadMenuBlurAlphaChanged -> {
-                    ReadConfig.readMenuBlurAlpha = intent.value
-                    readSettingsRepository.setReadMenuBlurAlpha(intent.value)
+                    ReadConfig.menuAlpha = intent.value
+                    readSettingsRepository.setMenuAlpha(intent.value)
                     postEvent(EventBus.UPDATE_READ_ACTION_BAR, true)
                 }