feat: global shell — header, footer, sidebars, and layout integration

app/(order)/layout.tsx

@@ -1,3 +1,10 @@
+import { Header } from "@/components/header"
+
 export default function OrderLayout({ children }: { children: React.ReactNode }) {
-  return <div className="min-h-screen bg-muted/30">{children}</div>
+  return (
+    <div className="flex min-h-screen flex-col">
+      <Header />
+      <main className="flex-1 bg-muted/30">{children}</main>
+    </div>
+  )
 }