Add manual-import and download-access features

Introduce manual import workflow and download permission support. Adds a Prisma migration and schema field (users.download_access) to track per-user download access, and updates admin UI to toggle global and per-user download access. Implements new APIs: filesystem browse, manual-import endpoint, download-access settings, audiobook download-status, and on-demand download-token generation. Adds frontend components for manual import and related tests, plus documentation for the manual-import feature and the documentation-agent prompt. Key files: prisma/migrations/20260212000000_add_download_access_permission/migration.sql, prisma/schema.prisma, src/app/api/admin/filesystem/browse/route.ts, src/app/api/admin/manual-import/route.ts, src/app/api/admin/settings/download-access/route.ts, src/app/api/requests/[id]/download-token/route.ts, src/app/api/audiobooks/[asin]/download-status/route.ts, and updated admin users pages/components and permissions util.

src/lib/hooks/useRequests.ts

@@ -515,6 +515,25 @@ export function useEbookStatus(asin: string | null) {
   };
 }
 
+interface DownloadStatus {
+  downloadAvailable: boolean;
+  requestId: string | null;
+}
+
+export function useDownloadStatus(asin: string | null) {
+  const { accessToken } = useAuth();
+
+  const endpoint = accessToken && asin ? `/api/audiobooks/${asin}/download-status` : null;
+
+  const { data, isLoading } = useSWR<DownloadStatus>(endpoint, fetcher);
+
+  return {
+    downloadAvailable: data?.downloadAvailable ?? false,
+    requestId: data?.requestId ?? null,
+    isLoading,
+  };
+}
+
 export function useFetchEbookByAsin() {
   const { accessToken } = useAuth();
   const [isLoading, setIsLoading] = useState(false);