Add debug logging for directory title processing

- Add debug output to getDirectoryListing() method
- Add debug_page_title to template data for troubleshooting
- Investigate why directory listings show 'Untitled' in footer
- Directory content shows correct H1 title but page_title is wrong

engine/templates/assets/footer.mustache

@@ -6,6 +6,7 @@
                     <div class="file-info">
                         <i class="bi bi-file-text"></i>
                         <span class="page-title" title="{{page_title}}">{{page_title}}</span>
+                        <!-- DEBUG: Raw title: {{debug_page_title}} -->
                         {{{file_info_block}}}
                     </div>
                     <div class="site-info">