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/components/RepoCodeFrequency.vue

@@ -144,7 +144,7 @@ const options: ChartOptions<'line'> = {
 
 <template>
   <div>
-    <div class="ui header tw-flex tw-items-center tw-justify-between">
+    <div class="ui header">
       {{ isLoading ? locale.loadingTitle : errorText ? locale.loadingTitleFailed: `Code frequency over the history of ${repoLink.slice(1)}` }}
     </div>
     <div class="tw-flex ui segment main-graph">

web_src/js/components/RepoContributors.vue

@@ -339,7 +339,7 @@ export default defineComponent({
 </script>
 <template>
   <div>
-    <div class="ui header tw-flex tw-items-center tw-justify-between">
+    <div class="ui header flex-left-right">
       <div>
         <relative-time
           v-if="xAxisMin && xAxisMin > 0"

web_src/js/components/RepoRecentCommits.vue

@@ -122,7 +122,7 @@ const options: ChartOptions<'bar'> = {
 
 <template>
   <div>
-    <div class="ui header tw-flex tw-items-center tw-justify-between">
+    <div class="ui header">
       {{ isLoading ? locale.loadingTitle : errorText ? locale.loadingTitleFailed: "Number of commits in the past year" }}
     </div>
     <div class="tw-flex ui segment main-graph">