feat(data-management): 添加数据集相似度推荐功能

- 在DatasetApplicationService中实现getSimilarDatasets方法，支持基于标签匹配的相似数据集推荐
- 新增normalizeSimilarLimit、normalizeTagNames、countSharedTags等辅助方法用于相似度计算
- 在DatasetRepository接口及其实现类中添加findSimilarByTags方法，支持数据库层面的标签匹配查询
- 在DatasetController中暴露/similar REST API端点，支持按需获取相似数据集
- 在前端Overview组件中展示相似数据集表格，包含名称、标签、类型、文件数和更新时间等信息
- 在DatasetDetail页面集成相似数据集获取逻辑，限制默认返回数量为4条
- 移除KnowledgeItem中的冗余title字段，统一使用其他标识信息
- 优化知识管理相关组件中的标题显示逻辑，移除硬编码标题值

frontend/src/pages/KnowledgeManagement/Detail/KnowledgeSetDetail.tsx

@@ -205,7 +205,7 @@ const KnowledgeSetDetail = () => {
       return;
     }
     setReadItemId(record.id);
-    setReadTitle(record.title || "知识条目");
+    setReadTitle("知识条目");
 
     if (!record.sourceDatasetId || !record.sourceFileId) {
       const content = record.content || "";

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

@@ -170,8 +170,8 @@ export default function KnowledgeItemEditor({
         {!isCreateMode && isFileItem && (
           <Form.Item label="文件">
             <div className="flex items-center gap-2">
-              <span className="truncate" title={data?.sourceFileId || data?.title}>
-                {data?.sourceFileId || data?.title || "-"}
+              <span className="truncate" title={data?.sourceFileId || "-"}>
+                {data?.sourceFileId || "-"}
               </span>
               <Button size="small" onClick={handleDownloadFile} disabled={readOnly}>
                 下载

frontend/src/pages/KnowledgeManagement/knowledge-management.const.tsx

@@ -92,7 +92,6 @@ export type KnowledgeSetView = {
 export type KnowledgeItemView = {
   id: string;
   setId: string;
-  title: string;
   content: string;
   contentType: KnowledgeContentType;
   status: KnowledgeStatusMeta | null;
@@ -140,7 +139,6 @@ export function mapKnowledgeItem(data: KnowledgeItem): KnowledgeItemView {
   return {
     id: data.id,
     setId: data.setId,
-    title: data.title,
     content: data.content,
     contentType: data.contentType,
     status: knowledgeStatusMap[data.status] ?? null,

frontend/src/pages/KnowledgeManagement/knowledge-management.model.ts

@@ -48,7 +48,6 @@ export interface KnowledgeSet {
 export interface KnowledgeItem {
   id: string;
   setId: string;
-  title: string;
   content: string;
   contentType: KnowledgeContentType;
   status: KnowledgeStatusType;