feat(knowledge): 添加知识条目文件预览和替换功能

- 后端实现知识条目文件预览接口，支持多种文件类型在线预览
- 后端实现知识条目文件替换功能，保留原有文件管理逻辑
- 前端新增文件预览模态框组件，支持文本、图片、音视频预览
- 前端知识条目编辑器添加文件替换上传功能
- 前端优化文件内容截断预览逻辑，统一使用工具函数处理
- 前端修复 PUT 请求中 FormData 处理问题，确保文件上传正常工作
- 新增文件预览相关工具函数和常量配置

frontend/src/pages/DataManagement/Detail/useFilesOperation.ts

@@ -4,6 +4,7 @@ import type {
 } from "@/pages/DataManagement/dataset.model";
 import { App } from "antd";
 import { useState } from "react";
+import { PREVIEW_TEXT_MAX_LENGTH, resolvePreviewFileType, truncatePreviewText } from "@/utils/filePreview";
 import {
   deleteDatasetFileUsingDelete,
   downloadFileByIdUsingGet,
@@ -15,11 +16,6 @@ import {
 } from "../dataset.api";
 import { useParams } from "react-router";
 
-const MAX_PREVIEW_LENGTH = 50000;
-const TEXT_FILE_EXTENSIONS = [".json", ".jsonl", ".txt", ".csv", ".tsv", ".xml", ".md", ".yaml", ".yml"];
-const IMAGE_FILE_EXTENSIONS = [".jpg", ".jpeg", ".png", ".gif", ".bmp", ".webp", ".svg"];
-const VIDEO_FILE_EXTENSIONS = [".mp4", ".webm", ".ogg", ".mov", ".avi"];
-const AUDIO_FILE_EXTENSIONS = [".mp3", ".wav", ".ogg", ".aac", ".flac", ".m4a"];
 
 export function useFilesOperation(dataset: Dataset) {
   const { message } = App.useApp();
@@ -99,23 +95,6 @@ export function useFilesOperation(dataset: Dataset) {
     setSelectedFiles([]); // 清空选中状态
   };
 
-  const resolvePreviewFileType = (fileName?: string) => {
-    const lowerName = (fileName || "").toLowerCase();
-    if (TEXT_FILE_EXTENSIONS.some((ext) => lowerName.endsWith(ext))) {
-      return "text";
-    }
-    if (IMAGE_FILE_EXTENSIONS.some((ext) => lowerName.endsWith(ext))) {
-      return "image";
-    }
-    if (VIDEO_FILE_EXTENSIONS.some((ext) => lowerName.endsWith(ext))) {
-      return "video";
-    }
-    if (AUDIO_FILE_EXTENSIONS.some((ext) => lowerName.endsWith(ext))) {
-      return "audio";
-    }
-    return null;
-  };
-
   const handlePreviewFile = async (file: DatasetFile) => {
     const datasetId = dataset?.id || id;
     if (!datasetId) {
@@ -146,13 +125,7 @@ export function useFilesOperation(dataset: Dataset) {
           throw new Error("下载失败");
         }
         const text = await response.text();
-        if (text.length > MAX_PREVIEW_LENGTH) {
-          setPreviewContent(
-            `${text.slice(0, MAX_PREVIEW_LENGTH)}\n\n... (内容过长，仅显示前 ${MAX_PREVIEW_LENGTH} 字符)`
-          );
-        } else {
-          setPreviewContent(text);
-        }
+        setPreviewContent(truncatePreviewText(text, PREVIEW_TEXT_MAX_LENGTH));
         setPreviewVisible(true);
       } catch (error) {
         console.error("Preview file content error:", error);