优化文件上传逻辑，统一JWT令牌处理方式，简化请求头设置，提升代码可读性。

app/routes/documents._index.tsx

@@ -788,13 +788,14 @@ export default function DocumentsIndex() {
     try {
       setAttachmentUploading(true);
       
+      const jwtToken = (loaderData.frontendJWT as string | undefined) || (loaderData.userInfo?.frontend_jwt as unknown as string | undefined);
       const result = await appendContractAttachments(
         selectedDocumentId,
         attachmentFiles,
         attachmentMergeMode,
         true, // isReprocess
         attachmentRemark || undefined,
-        loaderData.frontendJWT as string | undefined
+        jwtToken
       );
 
       if (result.error) {
@@ -862,11 +863,12 @@ export default function DocumentsIndex() {
     try {
       setTemplateUploading(true);
       
+      const jwtToken = (loaderData.frontendJWT as string | undefined) || (loaderData.userInfo?.frontend_jwt as unknown as string | undefined);
       const result = await uploadContractTemplate(
         templateFile,
         selectedDocumentId,
         undefined, // comparisonId
-        loaderData.frontendJWT as string | undefined
+        jwtToken
       );
 
       if (result.error) {