feat(web): complete MVP0 public layout, banner, and SEO baseline

apps/web/src/components/public-header-banner.tsx

@@ -0,0 +1,25 @@
+import type { PublicHeaderBanner as PublicHeaderBannerData } from "@cms/db"
+import Link from "next/link"
+
+type PublicHeaderBannerProps = {
+  banner: PublicHeaderBannerData | null
+}
+
+export function PublicHeaderBanner({ banner }: PublicHeaderBannerProps) {
+  if (!banner) {
+    return null
+  }
+
+  return (
+    <div className="border-b border-amber-200 bg-amber-50">
+      <div className="mx-auto flex w-full max-w-6xl flex-wrap items-center justify-between gap-3 px-6 py-2 text-sm text-amber-900">
+        <p>{banner.message}</p>
+        {banner.ctaLabel && banner.ctaHref ? (
+          <Link href={banner.ctaHref} className="font-medium underline underline-offset-2">
+            {banner.ctaLabel}
+          </Link>
+        ) : null}
+      </div>
+    </div>
+  )
+}