Fix mobile view header menu expansion issue

[MukundXplore]

Problem

There is a known issue where the header menu does not expand when viewed on mobile devices. This affects the user experience, as mobile users cannot access navigation links from the header.

Suggested Fix

Since the project uses plain JavaScript, ensure that:

• The menu expansion is triggered by a click or tap event on the hamburger/menu icon.
• The JavaScript correctly toggles the visibility of the menu container (e.g., by adding/removing a class or toggling inline styles).
• All relevant event listeners are attached after the DOM is loaded.
• The expanded menu should close when a navigation link is clicked or when the user taps outside the menu (optional for better UX).

Example approach:

// Example: Add this after DOMContentLoaded
document.getElementById('menu-icon').addEventListener('click', function() {
  document.getElementById('menu-container').classList.toggle('expanded');
});

Ensure that the IDs or classes match your HTML structure.

Acceptance Criteria

• Tapping the menu icon expands/collapses the menu on mobile view.
• No regression in desktop view navigation.
• Code uses plain (vanilla) JavaScript only.