jhxk68cdy: Add the five approved button styles, the glossy icon button and a dev story page

src/app/dev/buttons/page.tsx

@@ -0,0 +1,19 @@
+// Dev-only story page for the button system (task jhxk68cdy). Not linked from
+// the app and returns 404 in production builds. Shows every style in both themes.
+import type { CSSProperties } from "react";
+import { notFound } from "next/navigation";
+import { ButtonGallery } from "@/components/ButtonGallery";
+
+export const metadata = { title: "Buttons (dev)" };
+
+const grid: CSSProperties = { display: "grid", gridTemplateColumns: "repeat(auto-fit, minmax(340px, 1fr))", minHeight: "100vh" };
+
+export default function ButtonsDevPage() {
+  if (process.env.NODE_ENV === "production") notFound();
+  return (
+    <main style={grid}>
+      <ButtonGallery theme="dark" />
+      <ButtonGallery theme="light" />
+    </main>
+  );
+}