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/user/notification/notification_div.tmpl

@@ -3,7 +3,7 @@
 		{{$statusUnread := 1}}{{$statusRead := 2}}{{$statusPinned := 3}}
 		{{$notificationUnreadCount := call .PageGlobalData.GetNotificationUnreadCount}}
 		{{$pageTypeIsRead := eq $.PageType "read"}}
-		<div class="flex-text-block tw-justify-between tw-mb-[--page-spacing]">
+		<div class="flex-left-right tw-mb-[--page-spacing]">
 			<div class="small-menu-items ui compact tiny menu">
 				<a class="{{if not $pageTypeIsRead}}active{{end}} item" href="{{AppSubUrl}}/notifications?type=unread">
 					{{ctx.Locale.Tr "notification.unread"}}