Repo homepage styling tweaks (#33289)

Reduce it to a value that results in `.repo-home-sidebar-top` and
`.repo-home-sidebar-bottom` having 240px content width, the same as
GitHub.

Before:
<img width="1333" alt="Screenshot 2025-01-15 at 18 28 34"
src="https://github.com/user-attachments/assets/cf0fa21b-87be-40e3-a6cd-26d146bce9cc"
/>

After:
<img width="1330" alt="Screenshot 2025-01-15 at 18 28 27"
src="https://github.com/user-attachments/assets/28acd837-10f4-4176-b8a0-510cd28c8b8d"
/>

templates/repo/home_sidebar_top.tmpl

@@ -1,5 +1,5 @@
 <div class="repo-home-sidebar-top">
-	<form class="ignore-dirty tw-flex tw-flex-1 tw-mt-1" action="{{.RepoLink}}/search" method="get">
+	<form class="ignore-dirty tw-flex tw-flex-1" action="{{.RepoLink}}/search" method="get">
 		<div class="ui small action input tw-flex-1">
 			<input name="q" size="10" placeholder="{{ctx.Locale.Tr "search.code_kind"}}"> {{template "shared/search/button"}}
 		</div>

templates/repo/sub_menu.tmpl

@@ -1,5 +1,5 @@
 {{if and (not .HideRepoInfo) (not .IsBlame)}}
-<div class="ui segments repository-summary tw-mt-1 tw-mb-0">
+<div class="ui segments repository-summary tw-my-0">
 	<div class="ui segment sub-menu repository-menu">
 		{{if and (.Permission.CanRead ctx.Consts.RepoUnitTypeCode) (not .IsEmptyRepo)}}
 			<a class="item muted {{if .PageIsCommits}}active{{end}}" href="{{.RepoLink}}/commits/{{.RefFullName.RefWebLinkPath}}">

web_src/css/repo/home.css

@@ -1,7 +1,8 @@
 .repo-grid-filelist-sidebar {
   display: grid;
-  grid-template-columns: auto 300px;
+  grid-template-columns: auto 280px;
   grid-template-rows: auto auto 1fr;
+  gap: var(--page-spacing);
 }
 
 .repo-home-filelist {
@@ -13,13 +14,11 @@
 .repo-home-sidebar-top {
   grid-column: 2;
   grid-row: 1;
-  padding-left: 1em;
 }
 
 .repo-home-sidebar-bottom {
   grid-column: 2;
   grid-row: 2;
-  padding-left: 1em;
 }
 
 .repo-home-sidebar-bottom .flex-list > :first-child {