/* V29 — Menú móvil fijo + botón volver arriba */
@media(max-width:900px){
  .site-header{
    position:fixed!important;
    top:0;left:0;right:0;
    z-index:2000;
  }
  .desktop-nav.mobile-open{
    position:absolute;
    top:100%;
    left:0;right:0;
  }
  .back-to-top{
    position:fixed;
    right:18px;
    bottom:18px;
    z-index:1900;
    display:inline-flex;
    align-items:center;
    justify-content:center;
    min-width:48px;
    height:44px;
    padding:0 15px;
    border:1px solid rgba(241,239,233,.25);
    background:#17283a;
    color:#fff;
    font-size:10px;
    font-weight:700;
    letter-spacing:.08em;
    text-transform:uppercase;
    text-decoration:none;
    opacity:0;
    visibility:hidden;
    transform:translateY(10px);
    transition:opacity .2s ease, transform .2s ease, visibility .2s ease;
  }
  .back-to-top.is-visible{
    opacity:1;
    visibility:visible;
    transform:translateY(0);
  }
}
@media(min-width:901px){
  .back-to-top{display:none!important;}
}