fix(frontend): align search and header components with reference

assets/css/frontend/base.css

@@ -107,13 +107,7 @@ main.container,
  * math), so the card container gets no extra gutter either. The
  * <=991.98px media rule below restores 15px for every .container. */
 
-/* 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;
- * vendor CSS pins it at <=640px / .sidebar / .mobile-nav-widget only. */
-.header-slider-card .icon-cover-card {
-  font-size: 12px;
-}
+/* Let the reference .px12-sm utility apply at its mobile breakpoint only. */
 
 /* Keep the header multifunction search stable across route-specific CSS.
  * Some routes load a later .abs-right utility, while the global input focus