[dark-mode] Fix: Initialize ThemeToggle module in docReady

The ThemeToggle module was instantiated but never initialized, causing the
theme toggle button to be non-functional in the UI. The module's init()
method is now called during document ready, ensuring the button properly
listens for clicks and updates the theme.

This was the final blocker preventing dark mode toggle from working in
the deployed application.

Author: Hunta

src/frontend/js/app.js

@@ -46,10 +46,18 @@ class Docs {
     });
 
     console.log('CodeX Docs initialized');
+  }
+
+  /**
+   * Initialize theme toggle module
+   */
+  initThemeToggle() {
+    this.themeToggle.init();
   }  /**
    * Document is ready
    */
   docReady() {
+    this.initThemeToggle();
     this.moduleDispatcher = new ModuleDispatcher({
       Library: this,
     });