Description

This PR addresses an issue with the collapsible menu where the menu wouldn't expand properly after a page reload. The root cause was the incorrect calculation of max-height.

Closes #2265

Key Changes:

1. Fixed the calculation of max-height by using the scrollHeight property.
2. Updated the CSS box-sizing property to content-box to ensure padding is included in the element's overall size, resolving layout issues when expanding the menu.

These changes ensure that the menu expands and collapses smoothly, both after a reload and on user interaction.

Checklist

• I have read the Contribution Guidelines
• I have performed a self-review of my own code
• I have attached images of the change if it is UI based
• I have commented my code, particularly in hard-to-understand areas
• If my code has heavily changed functionality I have updated relevant docs on Stirling-PDFs doc repo
• My changes generate no new warnings
• I have read the section Add New Translation Tags (for new translation tags only)