feat: 添加剪裁背景相关组件及版本更新

- 新增BackgroundRadioButton自定义单选按钮组件
- 新增CustomApplicationBackground应用背景管理类
- 更新build.properties版本构建号(0->19)
- 完善封面剪裁背景修改功能相关基础设施

gallery/build.properties

@@ -1,8 +1,8 @@
 #Created by .winboll/winboll_app_build.gradle
-#Fri May 01 21:09:33 HKT 2026
+#Sat May 02 10:32:03 CST 2026
 stageCount=16
 libraryProject=
 baseVersion=15.0
 publishVersion=15.0.15
-buildCount=0
+buildCount=19
 baseBetaVersion=15.0.16

gallery/src/main/java/cc/winboll/studio/gallery/views/BackgroundRadioButton.java

@@ -0,0 +1,34 @@
+package cc.winboll.studio.gallery.views;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.widget.RadioButton;
+
+public class BackgroundRadioButton extends RadioButton {
+
+    CustomApplicationBackground mCustomApplicationBackground;
+
+    public BackgroundRadioButton(Context context) {
+        super(context);
+    }
+
+    public BackgroundRadioButton(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public BackgroundRadioButton(Context context, AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+    }
+
+    public void setupCustomApplicationBackground(Context context, int resId) {
+        mCustomApplicationBackground = new CustomApplicationBackground(context, resId);
+    }
+
+    public void setCustomApplicationBackground(CustomApplicationBackground customApplicationBackground) {
+        mCustomApplicationBackground = customApplicationBackground;
+    }
+
+    public CustomApplicationBackground getCustomApplicationBackground() {
+        return mCustomApplicationBackground;
+    }
+}

gallery/src/main/java/cc/winboll/studio/gallery/views/CustomApplicationBackground.java

@@ -0,0 +1,29 @@
+package cc.winboll.studio.gallery.views;
+
+import android.content.Context;
+import android.graphics.drawable.ColorDrawable;
+import android.graphics.drawable.Drawable;
+
+public class CustomApplicationBackground {
+    Drawable mDrawable;
+
+    public CustomApplicationBackground(Drawable drawable) {
+        mDrawable = drawable;
+    }
+
+    public CustomApplicationBackground(int color) {
+        mDrawable = new ColorDrawable(color);
+    }
+
+    public CustomApplicationBackground(Context context, int resId) {
+        mDrawable = context.getDrawable(resId);
+    }
+
+    public Drawable getDrawable() {
+        return mDrawable;
+    }
+
+    public void setDrawable(Drawable drawable) {
+        mDrawable = drawable;
+    }
+}