refactor(entity): 优化实体类字段描述

- 更新 image 实体类字段描述，明确各字段含义
- 修改 MarkdownFile 实体类字段描述，提高字段可理解性

biji-houdaun/src/main/java/com/test/bijihoudaun/entity/MarkdownFile.java

@@ -21,11 +21,11 @@ public class MarkdownFile {
     @Schema(description = "文本标题",implementation = String.class)
     private String title;
 
-    @Schema(description = "文本内容",implementation = String.class)
+    @Schema(description = " 文件名（带.md后缀），用于存储和识别",implementation = String.class)
     @TableField("file_name")
     private String fileName;
 
-    @Schema(description = "文本内容",implementation = String.class)
+    @Schema(description = "Markdown内容，存储实际文档内容",implementation = String.class)
     private String content;
     @Schema(description = "创建时间",implementation = LocalDateTime.class)
     private LocalDateTime createdAt;