feat(annotation): 添加标注任务的数据量统计功能

- 在前端表格中新增数据量和已标注列显示
- 添加标注完成百分比计算和提示功能
- 在后端schema中增加totalCount和annotatedCount字段
- 实现项目统计数据查询服务方法
- 集成前后端数据映射和接口响应更新

frontend/src/pages/DataAnnotation/Home/DataAnnotation.tsx

@@ -160,6 +160,30 @@ export default function DataAnnotation() {
       key: "datasetName",
       width: 180,
     },
+    {
+      title: "数据量",
+      dataIndex: "totalCount",
+      key: "totalCount",
+      width: 100,
+      align: "center" as const,
+    },
+    {
+      title: "已标注",
+      dataIndex: "annotatedCount",
+      key: "annotatedCount",
+      width: 100,
+      align: "center" as const,
+      render: (value: number, record: any) => {
+        const total = record.totalCount || 0;
+        const annotated = value || 0;
+        const percent = total > 0 ? Math.round((annotated / total) * 100) : 0;
+        return (
+          <span title={`${annotated}/${total} (${percent}%)`}>
+            {annotated}
+          </span>
+        );
+      },
+    },
     {
       title: "创建时间",
       dataIndex: "createdAt",