Add logout button to the sidebar

dental-server/public/app.js

@@ -34,6 +34,12 @@ function showErrorBanner(msg, detail = '') {
     setTimeout(() => banner && banner.remove(), 8000);
 }
 
+function logout() {
+    localStorage.removeItem('auth_token');
+    localStorage.removeItem('token');
+    window.location.href = '/login';
+}
+
 function getAuthToken() {
     return localStorage.getItem('auth_token');
 }