feat(image): 优化图片上传和预览功能

- 修改图片上传接口，支持用户 ID 和 Markdown ID 参数
- 实现在线预览功能，支持多种文件类型
- 优化图片插入到 Markdown 编辑器的逻辑
- 更新数据库配置和连接字符串

biji-houdaun/src/main/java/com/test/bijihoudaun/service/ImageService.java

@@ -14,7 +14,7 @@ public interface ImageService extends IService<Image> {
      * @return 上传的图片对象
      * @throws IOException 文件操作异常
      */
-    Image uploadImage(MultipartFile file) throws IOException;
+    Image uploadImage(MultipartFile file, Long userId, Long markdownId) throws IOException;
 
     /**
      * 删除图片

biji-houdaun/src/main/java/com/test/bijihoudaun/service/impl/ImageServiceImpl.java

@@ -33,7 +33,7 @@ public class ImageServiceImpl
     private ImageMapper imageMapper;
 
     @Override
-    public Image uploadImage( MultipartFile file) throws IOException {
+    public Image uploadImage( MultipartFile file, Long userId, Long markdownId) throws IOException {
         // 创建上传目录
         Path uploadPath = Paths.get(uploadDir);
         if (!Files.exists(uploadPath)) {
@@ -53,10 +53,11 @@ public class ImageServiceImpl
         Image image = new Image();
         image.setOriginalName(originalFilename);
         image.setStoredName(storedName);
-        image.setUrl("/uploads/" + storedName);
+        image.setUrl("/api/images/preview/" + storedName);
         image.setSize(file.getSize());
         image.setContentType(file.getContentType());
         image.setCreatedAt(new Date());
+        image.setMarkdownId(markdownId);
 
         this.save(image);
         return image;