feat: 文件上传接口直接返回完整 URL + 提现 content 改为非必填

- FileUploadResponse / FileUploadCompleteResponse 精简为只返回 url
- S3Store.BuildObjectURL 拼接完整访问地址
- 提现 method=0 时 content 不再参与必填校验
- 新增用户端 API 接口文档

internal/logic/public/file/fileuploadcompletelogic.go

@@ -61,11 +61,6 @@ func (l *FileUploadCompleteLogic) FileUploadComplete(req *types.FileUploadComple
 	}
 
 	return &types.FileUploadCompleteResponse{
-		FileId:      meta.FileID,
-		ObjectKey:   meta.ObjectKey,
-		Size:        head.ContentLength,
-		ContentType: head.ContentType,
-		Etag:        head.ETag,
-		Status:      meta.Status,
+		Url: l.svcCtx.S3Store.BuildObjectURL(meta.ObjectKey),
 	}, nil
 }