feat(knowledge): 添加知识条目导出功能和文件上传支持

- 在 KnowledgeItemApplicationService 中新增 exportKnowledgeItems 方法实现知识条目导出
- 添加 export 相关常量配置包括文件名格式、内容类型等
- 在 KnowledgeItemRepository 中新增 findAllBySetId 查询方法
- 在 KnowledgeItemController 中新增 export 接口端点
- 在 KnowledgeItemEditor 组件中添加文件上传功能支持 txt/md/markdown 格式
- 在 KnowledgeSetDetail 页面中添加导出按钮并集成导出 API
- 更新前端 API 文件添加 exportKnowledgeItemsUsingGet 方法
- 配置文件上传验证和自动填充标题内容逻辑

frontend/src/pages/KnowledgeManagement/components/KnowledgeItemEditor.tsx

@@ -1,5 +1,6 @@
 import { useEffect, useState } from "react";
-import { DatePicker, Form, Input, message, Modal, Select } from "antd";
+import { Button, DatePicker, Form, Input, message, Modal, Select, Upload, UploadFile } from "antd";
+import { UploadOutlined } from "@ant-design/icons";
 import dayjs from "dayjs";
 import {
   createKnowledgeItemUsingPost,
@@ -16,6 +17,26 @@ import {
 } from "../knowledge-management.model";
 import { queryDatasetTagsUsingGet } from "@/pages/DataManagement/dataset.api";
 
+const FILE_UPLOAD_ACCEPT = ".txt,.md,.markdown";
+const SUPPORTED_FILE_EXTENSIONS = new Set(["txt", "md", "markdown"]);
+const MARKDOWN_FILE_EXTENSIONS = new Set(["md", "markdown"]);
+
+const getFileExtension = (fileName: string) => {
+  const dotIndex = fileName.lastIndexOf(".");
+  return dotIndex > -1 ? fileName.slice(dotIndex + 1).toLowerCase() : "";
+};
+
+const stripFileExtension = (fileName: string) => {
+  const dotIndex = fileName.lastIndexOf(".");
+  if (dotIndex <= 0) {
+    return fileName;
+  }
+  return fileName.slice(0, dotIndex);
+};
+
+const resolveContentType = (extension: string) =>
+  MARKDOWN_FILE_EXTENSIONS.has(extension) ? KnowledgeContentType.MARKDOWN : KnowledgeContentType.TEXT;
+
 export default function KnowledgeItemEditor({
   open,
   setId,
@@ -33,6 +54,7 @@ export default function KnowledgeItemEditor({
 }) {
   const [form] = Form.useForm();
   const [tagOptions, setTagOptions] = useState<{ label: string; value: string }[]>([]);
+  const [fileList, setFileList] = useState<UploadFile[]>([]);
 
   const fetchTags = async () => {
     try {
@@ -77,9 +99,49 @@ export default function KnowledgeItemEditor({
           tags: [],
         });
       }
+      setFileList([]);
+    } else {
+      setFileList([]);
     }
   }, [open, data, form]);
 
+  const handleFileBeforeUpload = async (file: File) => {
+    const extension = getFileExtension(file.name);
+    if (!SUPPORTED_FILE_EXTENSIONS.has(extension)) {
+      message.error("仅支持 .txt/.md/.markdown 文件");
+      return Upload.LIST_IGNORE;
+    }
+
+    try {
+      const textContent = await file.text();
+      const currentTitle = form.getFieldValue("title");
+      form.setFieldsValue({
+        title: currentTitle || stripFileExtension(file.name),
+        content: textContent,
+        contentType: resolveContentType(extension),
+      });
+      setFileList([
+        {
+          uid: `${Date.now()}-${file.name}`,
+          name: file.name,
+          status: "done",
+          originFileObj: file,
+        },
+      ]);
+      message.success("文件已读取，可继续编辑内容");
+      return false;
+    } catch (error) {
+      console.error("读取文件失败", error);
+      message.error("读取文件失败，请重试");
+      return Upload.LIST_IGNORE;
+    }
+  };
+
+  const handleFileRemove = () => {
+    setFileList([]);
+    return true;
+  };
+
   const handleSubmit = async () => {
     try {
       const values = await form.validateFields();
@@ -107,6 +169,7 @@ export default function KnowledgeItemEditor({
       }
 
       form.resetFields();
+      setFileList([]);
       onSuccess();
     } catch {
       message.error("操作失败，请重试");
@@ -155,6 +218,21 @@ export default function KnowledgeItemEditor({
         >
           <Input.TextArea rows={8} placeholder="请输入内容" />
         </Form.Item>
+        {!data?.id && (
+          <Form.Item label="上传文件" extra="支持 .txt/.md/.markdown，将自动填充标题与内容">
+            <Upload
+              accept={FILE_UPLOAD_ACCEPT}
+              beforeUpload={handleFileBeforeUpload}
+              fileList={fileList}
+              maxCount={1}
+              onRemove={handleFileRemove}
+              showUploadList={{ showPreviewIcon: false }}
+              disabled={readOnly}
+            >
+              <Button icon={<UploadOutlined />}>选择文件</Button>
+            </Upload>
+          </Form.Item>
+        )}
         <div className="grid grid-cols-2 gap-4">
           <Form.Item label="领域" name="domain">
             <Input placeholder="请输入领域" />