fix(preview.html): correct back to parent directory link

Updated the "Back to Parent Directory" link to handle file paths
starting with a slash. This adjustment ensures the URL is properly
constructed, preventing broken links and enhancing navigation
usability in the preview view.

src/gitcloak/templates/preview.html

@@ -7,7 +7,7 @@
     <div class="col-md-12">
         <h1>{{ owner }}/{{ repo }} - <small>{{ file_path }}</small></h1>
         <div class="mb-3">
-            <a href="/{{ owner }}/{{ repo }}/tree/main/{{ file_path.rsplit('/', 1)[0] }}">
+            <a href="/{{ owner }}/{{ repo }}/tree/main/{{ ("/" + file_path).rsplit('/', 1)[0].lstrip("/") }}">
                 <img class="icon" src="/assets/dist/icons/folder.svg" alt="Back to Parent Directory"> Back to Parent Directory
             </a>
         </div>