Refactor frontend tw-justify-between layouts to flex-left-right (#37291)

This PR standardizes left/right two-child frontend layouts on
`flex-left-right` and removes ad-hoc `tw-justify-between` combinations.
The goal is consistent wrapping + spacing behavior under narrow widths
with less utility-class churn.

Also: remove useless "flex-center-wrap", slightly improve some templates
(no visual change, tested)

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: wxiaoguang <2114189+wxiaoguang@users.noreply.github.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/js/features/repo-issue-content.ts

@@ -14,7 +14,7 @@ function showContentHistoryDetail(issueBaseUrl: string, commentId: string, histo
   const elDetailDialog = createElementFromHTML(`
 <div class="ui modal content-history-detail-dialog">
   ${svg('octicon-x', 16, 'close icon inside')}
-  <div class="header tw-flex tw-items-center tw-justify-between">
+  <div class="header flex-left-right">
     <div>${itemTitleHtml}</div>
     <div class="ui dropdown dialog-header-options tw-mr-8 tw-hidden">
       ${i18nTextOptions}