refactor(admin): move the file integrity pages to Twig
Three .phtml become @admin/file-integrity{,-snapshot-confirm,-scan-result}.twig, and the two outcomes of a scan move to @admin/pages/result.twig. The message about a consistent snapshot carries a <br>, so it is handed over as Markup.
The active item of the sidebar keeps travelling as sec_menu, the same key the Plates pages used: the panel is migrated page by page, and the menu contract stays put.
The active item of the sidebar keeps travelling as sec_menu, the same key the Plates pages used: the panel is migrated page by page, and the menu contract stays put.