Fix "The sidebar of the repository file list does not have a fixed height #34298" (#34321)

There is a known issue where scrolling to the bottom of the page is
affected by unknown elements in the footer area:

https://github.com/go-gitea/gitea/blob/24145f811069295b9727f25469f1dd3a7c2c5dd7/templates/base/footer.tmpl#L11-L18

![after](https://github.com/user-attachments/assets/4cdbce32-d22e-4907-a78b-c8e301017fac)

Author: kerwin612

templates/repo/view.tmpl

@@ -17,7 +17,7 @@
 		{{template "repo/code/recently_pushed_new_branches" .}}
 
 		<div class="repo-view-container">
-			<div class="repo-view-file-tree-container not-mobile {{if not .UserSettingCodeViewShowFileTree}}tw-hidden{{end}}" {{if .IsSigned}}data-user-is-signed-in{{end}}>
+			<div class="tw-flex tw-flex-col repo-view-file-tree-container not-mobile {{if not .UserSettingCodeViewShowFileTree}}tw-hidden{{end}}" {{if .IsSigned}}data-user-is-signed-in{{end}}>
 				{{template "repo/view_file_tree" .}}
 			</div>
 			<div class="repo-view-content">

web_src/css/repo/home.css

@@ -58,6 +58,11 @@
   flex: 0 0 15%;
   min-width: 0;
   max-height: 100vh;
+  position: sticky;
+  top: 0;
+  bottom: 0;
+  height: 100%;
+  overflow-y: hidden;
 }
 
 .repo-view-content {