feat: add background fill functionality for layers

- Implemented FillLayerBackgroundCommand to fill the background of layers with a specified color.
- Introduced BackgroundFillManager to manage background fill operations.
- Updated LayerManager to include fillLayerBackground method.
- Enhanced LayersPanel with a color picker for filling layer backgrounds.
- Modified RasterizeLayerCommand to reflect changes in terminology and functionality.
- Adjusted LayerSort to ensure filled layers are rendered at the correct z-index.
- Updated relevant utility functions and components to support new fill feature.

src/component/Canvas/CanvasEditor/utils/LayerSort.js

@@ -96,6 +96,10 @@ export class LayerSort {
    * @returns {number} 更新后的z-index
    */
   processLayerObjects(layer, currentZIndex, zIndexMap) {
+    if (layer.fill) {
+      // 如果图层有填充，则填充在最底层
+      zIndexMap.set(layer.fill.id, currentZIndex++);
+    }
     // 检查是否有子图层（组图层）
     if (layer.children?.length > 0) {
       // 处理每个子图层

src/component/Canvas/CanvasEditor/utils/layerUtils.js

@@ -1,4 +1,4 @@
-import { isArray } from "lodash-es";
+import { fill, isArray } from "lodash-es";
 
 /**
  * 图层关联工具类
@@ -193,6 +193,8 @@ export function simplifyLayers(layers) {
               .filter((obj) => obj !== null)
           : [],
       children: layer.children && isArray(layer.children) ? simplifyLayers(layer.children) : [],
+      fill: layer?.fill || null,
+      fillColor: layer.fillColor,
     };
 
     return simplifiedLayer;