feat: 添加笔刷指示器功能，支持动态显示当前笔刷大小和颜色；更新图层可擦除状态逻辑

src/component/Canvas/CanvasEditor/managers/CanvasManager.js

@@ -328,6 +328,26 @@ export class CanvasManager {
     this.canvas.renderAll();
   }
 
+  // 设置固定图层可擦除状态
+  setFixedLayerErasable({ type = "isFixed", flag = false }) {
+    const layer = this.layers.value.find((layer) => layer[type]);
+    if (layer) {
+      // 设置固定图层的可擦除状态
+      layer.locked = flag;
+      // 更新画布对象的erasable属性
+      const fabricObject = this.canvas
+        .getObjects()
+        .find((obj) => obj.id === layer.id);
+      if (fabricObject) {
+        fabricObject.erasable = flag;
+        fabricObject.set("erasable", flag);
+        fabricObject.setCoords(); // 更新控制点坐标
+        this.canvas.renderAll(); // 重新渲染画布
+      }
+      return;
+    }
+  }
+
   setCanvasSize(width, height) {
     this.width = width;
     this.height = height;