fix(header): drop card container gutter so header spans content width

The global .container is padding-free at >=992px (1200px dual-column
geometry), but the header slider card container re-added 15px side
padding, visibly insetting the icon cards ~15px per side relative to
the main content below. Zibll keeps header and content boxes equal by
sharing one container model; drop the local gutter so AKSRT does the
same. Mobile keeps its 15px via the <=991.98px media rule.

assets/css/build/public.css

@@ -2504,14 +2504,6 @@ main.container,
   --bs-gutter-y: 0;
 }
 
-/* Header multifunc icon cards need horizontal gutter (legacy content rows).
- * Global .container padding is 0 for dual-column float math. */
-.header-slider-card.container {
-  padding-left: 15px;
-  padding-right: 15px;
-  box-sizing: border-box;
-}
-
 /* Header multifunc icon cards: pin typography baseline so cards render
  * identically on all pages. .px12-sm is only defined globally in
  * legacy-utilities.css, which is @import'd by the single-post aggregator;