.site-header {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: flex-start;
  padding: 12px 16px;
}

.menu-toggle-btn {
  position: fixed;
  top: 14px;
  right: 16px;
  z-index: 1500;
  /* ... 以下すべて削除 ... */
}

.menu-toggle-btn .btn-text {
  display: none; /* テキストは消してアイコンのみに */
}

.nav-icon,
.nav-icon::before,
.nav-icon::after {

}
.nav-icon::before { position: absolute; top: -6px; }
.nav-icon::after { position: absolute; top: 6px; }

.bottom-nav {
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  background-color: #ffffff;
  border-top: 1px solid #e0e0e0;
  display: flex;
  justify-content: space-around;
  padding: 10px 0;
  z-index: 1000;
}