remove toggleUserMenu and userMenuOpen since they are no longer used

src/components/ModernNavbar.vue

@@ -182,7 +182,6 @@ const auth = useAuth()
 
 const sidebarCollapsed = ref(false)
 const mobileMenuOpen = ref(false)
-const userMenuOpen = ref(false)
 const isDarkMode = ref(false)
 
 function toggleSidebarCollapse() {
@@ -201,18 +200,10 @@ function updateBodyClass() {
 
 function toggleMobileMenu() {
   mobileMenuOpen.value = !mobileMenuOpen.value
-  if (mobileMenuOpen.value) {
-    userMenuOpen.value = false
-  }
 }
 
 function closeMobileMenu() {
   mobileMenuOpen.value = false
-  userMenuOpen.value = false
-}
-
-function toggleUserMenu() {
-  userMenuOpen.value = !userMenuOpen.value
 }
 
 function toggleTheme() {