added pubilc folder

frontend/public/js/nav.js

@@ -0,0 +1,52 @@
+(function () {
+  var burger = document.querySelector('.nav-burger');
+  var menu = document.getElementById('mobileMenu');
+  if (!burger || !menu) return;
+
+  function closeMenu() {
+    menu.hidden = true;
+    burger.classList.remove('is-open');
+    burger.setAttribute('aria-expanded', 'false');
+  }
+
+  function openMenu() {
+    menu.hidden = false;
+    burger.classList.add('is-open');
+    burger.setAttribute('aria-expanded', 'true');
+  }
+
+  burger.addEventListener('click', function () {
+    if (menu.hidden) {
+      openMenu();
+    } else {
+      closeMenu();
+    }
+  });
+
+  menu.addEventListener('click', function (e) {
+    if (e.target.tagName === 'A') {
+      closeMenu();
+    }
+  });
+
+  document.addEventListener('keydown', function (e) {
+    if (e.key === 'Escape') {
+      closeMenu();
+    }
+  });
+
+  document.addEventListener('click', function (e) {
+    if (!menu.hidden && !menu.contains(e.target) && !burger.contains(e.target)) {
+      closeMenu();
+    }
+  });
+
+  // Desktop CSS hides .mobile-menu entirely, but if the menu was left open
+  // on mobile and the viewport grows past the breakpoint (resize, rotate,
+  // devtools), reset state so it doesn't reopen collapsed at mobile width.
+  window.matchMedia('(min-width: 761px)').addEventListener('change', function (e) {
+    if (e.matches) {
+      closeMenu();
+    }
+  });
+})();