Add a beta label in the header

src/components/header.tsx

@@ -29,7 +29,7 @@ export function Header() {
   return (
     <header className="border-b">
       <div className="container mx-auto px-4 py-4 flex items-center justify-between">
-        <div className="flex items-center gap-2">
+        <div className="flex items-center gap-3">
           <Link href="/">
             <img
               src={logoSrc}
@@ -37,6 +37,9 @@ export function Header() {
               className="h-8 w-auto cursor-pointer"
             />
           </Link>
+          <span className="bg-yellow-500/20 text-yellow-500 text-xs font-bold px-2 py-1 rounded border border-yellow-500/50">
+            BETA TEST
+          </span>
         </div>
 
         <div className="flex items-center gap-2">