fix: increase flickable cache buffer for better performance

1. Added cacheBuffer property to Flickable component set to width * 2
2. This increases the off-screen rendering buffer to improve scrolling
performance
3. The buffer now extends two screen widths beyond visible area in both
directions
4. Helps prevent visual artifacts and stuttering during rapid scrolling

Influence:
1. Test smooth scrolling in fullscreen mode with various content types
2. Verify no performance degradation when scrolling quickly
3. Check memory usage doesn't increase excessively with larger cache
4. Test scrolling behavior at different screen resolutions
5. Verify no visual artifacts appear during scrolling transitions

fix: 增加Flickable缓存缓冲区以提升性能

1. 为Flickable组件添加cacheBuffer属性，设置为width * 2
2. 增加离屏渲染缓冲区以提高滚动性能
3. 缓冲区现在扩展到可见区域两侧各两个屏幕宽度
4. 有助于防止快速滚动时的视觉伪影和卡顿

Influence:
1. 在全屏模式下测试不同类型内容的平滑滚动
2. 验证快速滚动时性能不会下降
3. 检查内存使用不会因更大的缓存而过度增加
4. 在不同屏幕分辨率下测试滚动行为
5. 验证滚动过渡期间不会出现视觉伪影

PMS: BUG-354237

Author: wjyrich

qml/FullscreenFrame.qml

@@ -385,6 +385,7 @@ InputEventItem {
                     highlightMoveDuration: 200
                     highlightMoveVelocity: -1
                     boundsBehavior: Flickable.StopAtBounds
+                    cacheBuffer: width * 2
 
                     activeFocusOnTab: true
                     focus: true