chore: add reopen preview btn (#9279)

Co-authored-by: billsyli <billsyli@tencent.com>

web/app/components/datasets/create/step-two/index.tsx

       <div ref={scrollRef} className='relative h-full w-full overflow-y-scroll'>
         <div className={cn(s.pageHeader, scrolled && s.fixed, isMobile && '!px-6')}>
           <span>{t('datasetCreation.steps.two')}</span>
-          {isMobile && (
+          {(isMobile || !showPreview) && (
             <Button
               className='border-[0.5px] !h-8 hover:outline hover:outline-[0.5px] hover:outline-gray-300 text-gray-700 font-medium bg-white shadow-[0px_1px_2px_0px_rgba(16,24,40,0.05)]'
               onClick={setShowPreview}