feat: download button and page

src/app/downloads/page.tsx

@@ -0,0 +1,11 @@
+import { PageHeader } from "@/components/layout/PageHeader";
+import { DownloadManager } from "@/components/downloads/DownloadManager";
+
+export default function DownloadsPage() {
+  return (
+    <>
+      <PageHeader title="Téléchargements" description="Gérez vos livres disponibles hors ligne" />
+      <DownloadManager />
+    </>
+  );
+}