Use a light gray announcement bar instead of black

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WHUa6ik1KRSEFkF6ShUYpC

components/shopify/header.tsx

@@ -63,7 +63,7 @@ const Header: React.FC<HeaderProps> = ({
     <>
       {/* Sits above the sticky nav, so it scrolls away on its own. */}
       {announcement && (
-        <div className="bg-foreground text-background">
+        <div className="bg-muted text-foreground">
           <div className="max-w-screen-2xl mx-auto flex h-9 items-center justify-center px-8 text-center text-xs">
             {announcementUrl ? (
               <Link