query("SELECT a.*, r.nombre as responsable_nombre FROM actividades a LEFT JOIN responsables r ON a.responsable_id = r.id ORDER BY a.fecha_inicio, a.hora_inicio");
$actividades = $stmt->fetchAll(PDO::FETCH_ASSOC);
// This is just a placeholder, we will calculate this properly in a future step.
$total_actividades = count($actividades);
?>