fix(navigation): stop mangling zibsvg/customsvg menu icons

aksrt_render_menu_icon() prefixed any value without an fa substring
with fa fas fa-, turning picker values like zibsvg-hot into
fa fas fa-zibsvg-hot — blank icons in the frontend nav. Sprite and
inline SVG values now flow through aksrt_icon_markup with the
menu-item-icon classes attached; FA values keep the legacy padding.

inc/helpers/menu-decoration.php

@@ -45,20 +45,30 @@ function aksrt_get_menu_item_decoration($menu_item): array {
 }
 
 /**
- * @param string $icon_class FA5 icon class.
+ * @param string $icon_class Icon-picker value (FA5 class, zibsvg- or customsvg-).
  * @param bool   $enabled    Global switch.
  */
 function aksrt_render_menu_icon(string $icon_class, bool $enabled = true): string {
 	if (!$enabled || $icon_class === '') {
 		return '';
 	}
+
+	// Sprite/inline values must reach aksrt_icon_markup untouched — the legacy
+	// fa-prefix padding below would corrupt them (zibsvg-hot → fa fas fa-zibsvg-hot).
+	if (str_starts_with($icon_class, 'zibsvg-')) {
+		return aksrt_icon_markup($icon_class, 'icon mr3 menu-item-icon');
+	}
+	if (str_starts_with($icon_class, 'customsvg-')) {
+		return aksrt_icon_markup($icon_class, 'mr3 menu-item-icon');
+	}
+
 	// legacy uses the Font Awesome 5 `fa` prefix.
 	if (strpos($icon_class, 'fa') === false) {
 		$icon_class = 'fa fas fa-' . ltrim($icon_class, '-');
 	} elseif (strpos($icon_class, 'fa-') === 0 && strpos($icon_class, ' ') === false) {
 		$icon_class = 'fa ' . $icon_class;
 	}
-	return '<i class="' . esc_attr($icon_class) . ' mr3 menu-item-icon" aria-hidden="true"></i>';
+	return aksrt_icon_markup($icon_class, 'mr3 menu-item-icon');
 }
 
 /**