feat(admin): lay out the system check in cards with a summary
The checks were four bordered tables. A line on top now sums them up, and each group is a card of rows with a mark, the name, the value and the description under it. A failed check is marked by how much it matters, which the checker already told: a required one in red, a recommendation in amber, a note such as the accounts on the old password hash in blue rather than as an error.