feat: página de plantillas de correo + prueba de envío + bitácora

frontend/src/components/Sidebar.tsx

@@ -18,6 +18,7 @@ export default function Sidebar() {
     { href: "/settings/departments", icon: "bi-diagram-3", label: "Departamentos" },
     { href: "/settings/team", icon: "bi-people", label: "Equipo" },
     { href: "/settings/sla", icon: "bi-stopwatch", label: "SLA" },
+    { href: "/settings/email", icon: "bi-envelope", label: "Correo" },
   ];
 
   const isActive = (href: string) =>