优化代码健壮性，解决部分硬编码问题

sf_manufacturing/models/mrp_workorder.py

@@ -210,10 +210,14 @@ class ResMrpWorkOrder(models.Model):
 
         local_dir_path = '/ftp/before'
         os.makedirs(local_dir_path, exist_ok=True)
-        local_filename = 'WH_MO_00099.xls'
+        local_filename = self.save_name + '.xls'
         local_file_path = os.path.join(local_dir_path, local_filename)
         logging.info('local_file_path:%s' % local_file_path)
-        remote_path = '/home/ftp/ftp_root/ThreeTest/XT/Before/WH_MO_00099.xls'
+        remote_path = '/home/ftp/ftp_root/ThreeTest/XT/Before/' + local_filename
+        logging.info('remote_path:%s' % remote_path)
+
+        if not ftp.file_exists(remote_path):
+            raise UserError(f"文件不存在: {remote_path}")
 
         with open(local_file_path, 'wb') as local_file:
             ftp.ftp.retrbinary('RETR ' + remote_path, local_file.write)