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/settings/githook_edit.tmpl

@@ -1,7 +1,7 @@
 {{template "repo/settings/layout_head" (dict "ctxData" . "pageClass" "repository settings edit githook")}}
 	<div class="repo-setting-content">
 		<form class="ui form" action="{{.Link}}" method="post">
-			<h4 class="ui top attached header flex-text-block tw-justify-between tw-flex-wrap">
+			<h4 class="ui top attached header flex-left-right">
 				{{.Hook.Name}}
 				<div class="tw-font-normal tw-font-sans tw-text-base">
 					{{template "repo/editor/options" dict "CodeEditorConfig" $.CodeEditorConfig}}

templates/repo/settings/webhook/history.tmpl

@@ -17,7 +17,7 @@
 		<div class="ui list">
 			{{range .History}}
 				<div class="item">
-					<div class="flex-text-block tw-justify-between">
+					<div class="flex-left-right">
 						<div class="flex-text-inline">
 							{{if .IsSucceed}}
 								<span class="tw-text-green">{{svg "octicon-check"}}</span>