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/view_file.tmpl

@@ -13,7 +13,7 @@
 	{{end}}
 
 	{{if not .ReadmeInList}}
-		<div id="repo-file-commit-box" class="ui segment list-header tw-mb-4 tw-flex tw-justify-between">
+		<div id="repo-file-commit-box" class="ui segment list-header tw-mb-4 flex-left-right">
 			{{template "repo/latest_commit" .}}
 			{{if .LatestCommit}}
 				{{if .LatestCommit.Committer}}
@@ -25,7 +25,7 @@
 		</div>
 	{{end}}
 
-	<h4 class="file-header ui top attached header tw-flex tw-items-center tw-justify-between tw-flex-wrap">
+	<h4 class="file-header ui top attached header flex-left-right">
 		<div class="file-header-left tw-flex tw-items-center tw-py-2 tw-pr-4">
 			{{if .ReadmeInList}}
 				{{svg "octicon-book" 16 "tw-mr-2"}}