feat: 1.固定图层缩略图（完成）

2.工具栏新增插槽（完成）
3.loadJSON的元素顺序回发生错误

src/component/Canvas/CanvasEditor/commands/BackgroundCommands.js

@@ -33,7 +33,11 @@ export class CreateBackgroundLayerCommand extends Command {
     const bgObject = this._createBackgroundObject();
 
     // 将背景对象添加到图层中
-    this.backgroundLayer.fabricObject = bgObject;
+    this.backgroundLayer.fabricObject = bgObject.toObject([
+      "id",
+      "layerId",
+      "type",
+    ]);
 
     // 添加图层到最底部
     this.layers.value.push(this.backgroundLayer);

src/component/Canvas/CanvasEditor/commands/LayerCommands.js

@@ -3581,7 +3581,11 @@ export class ChangeFixedImageCommand extends Command {
               restoredImage.setCoords();
 
               // 更新引用
-              this.targetLayer.fabricObject = restoredImage;
+              this.targetLayer.fabricObject = restoredImage.toObject([
+                "id",
+                "layerId",
+                "type",
+              ]);
               this.layerManager.updateLayerObject(
                 this.targetLayer.id,
                 restoredImage

src/component/Canvas/CanvasEditor/commands/RedGreenCommands.js

@@ -358,7 +358,7 @@ export class BatchInitializeRedGreenModeCommand extends Command {
 
       this.canvas.add(object);
       this.canvas.sendToBack(object);
-      backgroundLayer.fabricObject = object;
+      backgroundLayer.fabricObject = object.toObject(["id", "layerId", "type"]);
     } else {
       // 更新现有背景对象大小
       object.set({