perf(agent): 为历史对话项添加 key 属性

- 在 history-item 组件中添加 :key="index"，以优化渲染性能

src/views/agent/work-flow/components/DynamicForm.vue

@@ -21,7 +21,7 @@
           v-model="formData[field.props.name]"
           :placeholder="field?.props?.placeholder"
         />
-        <a-color-picker       v-if="field.type === 'color_picker'"
+        <a-color-picker    v-if="field.type === 'color_picker'"
                               style="width: 500px; height: 200px"
                               v-model="formData[field.props.name]" />
         <ImageUpload