feat(biji-houdaun): 实现用户注册、登录、 Markdown 文件和图片上传功能

- 新增用户注册、登录接口及服务实现
- 添加 Markdown 文件创建、更新接口及服务实现
- 实现图片上传、获取接口及服务实现
- 集成 Snowflake ID 生成器
- 添加全局异常处理和统一返回结果封装
- 配置跨域访问和静态资源处理
- 实现基础的 XSS 防护

biji-houdaun/src/main/java/com/test/bijihoudaun/controller/ImageController.java

@@ -0,0 +1,33 @@
+package com.test.bijihoudaun.controller;
+
+
+import com.test.bijihoudaun.entity.Image;
+import com.test.bijihoudaun.service.ImageService;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+import org.springframework.web.multipart.MultipartFile;
+
+import java.io.IOException;
+
+@RestController
+@RequestMapping("/api/images")
+public class ImageController {
+
+    @Autowired
+    private ImageService imageService;
+
+    @PostMapping
+    public ResponseEntity<Image> uploadImage(
+            @RequestParam Integer userId,
+            @RequestParam(required = false) Integer markdownId,
+            @RequestParam("file") MultipartFile file) {
+
+        try {
+            Image image = imageService.uploadImage(userId, markdownId, file);
+            return ResponseEntity.ok(image);
+        } catch (IOException e) {
+            return ResponseEntity.status(500).build();
+        }
+    }
+}