feat(upload): 修改大文件上传合并接口

- 将合并接口返回类型从 AjaxResult 更改为 R<Map<String, String>>
- 使用 Map 结构封装文件 URL、原始文件名和 OSS ID
- 统一异常处理，失败时返回 R.fail 包装的错误信息
- 添加 ossId 转换为字符串类型的处理逻辑
- 引入 R 类和相关工具类支持新的返回结构

ruoyi-admin/src/main/java/com/ruoyi/web/controller/common/BigUploadController.java

@@ -1,15 +1,19 @@
 package com.ruoyi.web.controller.common;
 
 import com.ruoyi.common.core.AjaxResult;
+import com.ruoyi.common.core.domain.R;
 import com.ruoyi.system.domain.vo.SysOssVo;
 import com.ruoyi.web.service.ChunkedUploadService;
 import lombok.RequiredArgsConstructor;
+import org.redisson.api.RMap;
 import org.springframework.http.MediaType;
 import org.springframework.validation.annotation.Validated;
 import org.springframework.web.bind.annotation.*;
 import org.springframework.web.multipart.MultipartFile;
 
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 @Validated
 @RestController
@@ -53,17 +57,18 @@ public class BigUploadController {
      * @return 合并结果及文件信息
      */
     @PostMapping("/merge")
-    public AjaxResult merge(@RequestParam("fileMd5") String fileMd5,
-                            @RequestParam("fileName") String fileName,
-                            @RequestParam("totalChunks") int totalChunks) {
+    public R<Map<String, String>> merge(@RequestParam("fileMd5") String fileMd5,
+                                      @RequestParam("fileName") String fileName,
+                                      @RequestParam("totalChunks") int totalChunks) {
         try {
             SysOssVo oss = chunkedUploadService.mergeChunks(fileMd5, fileName, totalChunks);
-            return AjaxResult.success()
-                .put("url", oss.getUrl())
-                .put("fileName", oss.getOriginalName())
-                .put("ossId", oss.getOssId());
+            Map<String, String> map = new HashMap<>(2);
+            map.put("url", oss.getUrl());
+            map.put("fileName", oss.getOriginalName());
+            map.put("ossId", oss.getOssId().toString());
+            return R.ok(map);
         } catch (Exception e) {
-            return AjaxResult.error(e.getMessage());
+            return R.fail(e.getMessage());
         }
     }
     /**