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>

templates/repo/pulls/status.tmpl

@@ -21,7 +21,7 @@
 	</div>
 
 	{{if and $statusCheckData $statusCheckData.RequireApprovalRunCount}}
-		<div class="ui attached segment flex-text-block tw-justify-between" id="approve-status-checks">
+		<div class="ui attached segment flex-left-right" id="approve-status-checks">
 			<div>
 				<strong>
 					{{ctx.Locale.Tr "repo.pulls.status_checks_need_approvals" $statusCheckData.RequireApprovalRunCount}}