fix(upload): 修复流式上传中的文件名处理逻辑

- 修正预上传接口调用时传递正确的文件总数而非固定值-1
- 移除导入配置中文件分割时的文件扩展名保留逻辑
- 删除流式上传选项中的fileExtension参数定义
- 移除流式上传实现中的文件扩展名处理相关代码
- 简化新文件名生成逻辑，不再附加扩展名后缀

frontend/src/utils/file.util.ts

@@ -403,7 +403,6 @@ export function readFileAsText(
 export interface StreamUploadOptions {
   reqId: number;
   fileNamePrefix?: string;
-  fileExtension?: string;
   hasArchive?: boolean;
   prefix?: string;
   signal?: AbortSignal;
@@ -423,7 +422,7 @@ export async function streamSplitAndUpload(
   chunkSize: number = 1024 * 1024, // 1MB
   options: StreamUploadOptions
 ): Promise<StreamUploadResult> {
-  const { reqId, fileNamePrefix, fileExtension = ".txt", prefix, signal, maxConcurrency = 3 } = options;
+  const { reqId, fileNamePrefix, prefix, signal, maxConcurrency = 3 } = options;
   
   const fileSize = file.size;
   let offset = 0;
@@ -434,7 +433,6 @@ export async function streamSplitAndUpload(
   
   // 获取文件名基础部分
   const baseName = fileNamePrefix || file.name.replace(/\.[^/.]+$/, "");
-  const ext = fileExtension.startsWith(".") ? fileExtension : `.${fileExtension}`;
   
   // 用于并发控制的队列
   const uploadQueue: Promise<void>[] = [];
@@ -449,7 +447,7 @@ export async function streamSplitAndUpload(
       return;
     }
 
-    const newFileName = `${baseName}_${String(index + 1).padStart(6, "0")}${ext}`;
+    const newFileName = `${baseName}_${String(index + 1).padStart(6, "0")}`;
     const blob = new Blob([line], { type: "text/plain" });
     const lineFile = new File([blob], newFileName, { type: "text/plain" });