feat: implement tenant impersonation for super admins

- Added POST /api/impersonate/:tenantId to generate a specialized tenant-scoped JWT.

- Added UI button in SuperAdmin page to trigger impersonation.

- Saved original super_admin token to localStorage to allow returning without re-login.

- Added 'Retornar ao Painel Central' button in sidebar to quickly revert to super admin status.

components/Layout.tsx

@@ -7,7 +7,7 @@ import {
 import { 
   getAttendances, getUsers, getUserById, logout, searchGlobal, 
   getNotifications, markNotificationAsRead, markAllNotificationsAsRead,
-  deleteNotification, clearAllNotifications
+  deleteNotification, clearAllNotifications, returnToSuperAdmin
 } from '../services/dataService';
 import { User } from '../types';
 
@@ -212,7 +212,19 @@ export const Layout: React.FC<{ children: React.ReactNode }> = ({ children }) =>
           </nav>
 
           {/* User Profile Mini - Now Clickable to Profile */}
-          <div className="p-4 border-t border-zinc-100 dark:border-dark-border">
+          <div className="p-4 border-t border-zinc-100 dark:border-dark-border space-y-3">
+            {localStorage.getItem('ctms_super_admin_token') && (
+              <button
+                onClick={() => {
+                  if (returnToSuperAdmin()) {
+                    window.location.href = '/';
+                  }
+                }}
+                className="w-full flex items-center justify-center gap-2 py-2 px-3 bg-zinc-900 dark:bg-brand-yellow text-white dark:text-zinc-950 rounded-lg text-xs font-bold hover:opacity-90 transition-colors"
+              >
+                Retornar ao Painel Central
+              </button>
+            )}
             <div className="flex items-center gap-3 p-2 rounded-lg bg-zinc-50 dark:bg-dark-bg/50 border border-zinc-100 dark:border-dark-border group">
               <div 
                 onClick={() => navigate('/profile')}