fix(nav): kill Bootstrap 5 navbar padding so bar matches zibll height

AKSRT loads BS5 (.navbar --bs-navbar-padding-y:.5rem) while zibll uses
BS3 without it; that alone added ~16px. Zero BS navbar pad, keep only
.header 8px 20px (mobile 0 8px), horizontal CTA margins, tighter mobile
logo/toggle row.

assets/css/frontend/nav/header-menu-buttons.css

@@ -43,7 +43,7 @@
   width: fit-content !important;
   max-width: fit-content !important;
   min-width: 0 !important;
-  margin: 0.4em !important;
+  margin: 0 0.4em !important;
   appearance: none;
   -webkit-appearance: none;
   cursor: pointer;