Fix dynamic favicon path handling using root URL

- Updated favicon handling to dynamically set the favicon path based on the root URL.
- Fixed the issue in the commit  245ea8c where favicon would not load correctly on subdirectory pages by calculating the site root URL using window location.

Fixes sugarlabs#507

js/main.js

@@ -23,13 +23,16 @@ $(document).ready(function () {
         if (logoID < 10) {
             logoID = "0" + logoID;
         }
-
-        // Extract the base path from the current favicon href
-        var currentHref = defaultIcon.getAttribute('href');
-        var basePath = currentHref.substring(0, currentHref.lastIndexOf('/') + 1);
 
-        // Update only the filename portion while keeping the original path
-        defaultIcon.href = basePath + 'favicon_' + logoID + '.png';
+        var rootUrl = '';
+        var baseTag = document.querySelector('base');
+        if (baseTag && baseTag.href) {
+            rootUrl = baseTag.href;
+        } else {
+            rootUrl = window.location.protocol + '//' + window.location.host + '/';
+        }
+
+        defaultIcon.href = rootUrl + 'assets/favicon_' + logoID + '.png';
     }
 
     var h = document.querySelector('.logo1').innerHTML;