Settings, your website and clients follow their permissions

The last of the switches in Roles & Permissions now do what they say, for every role.

Settings, the website and the booking widget — switch one off and that role can look but not change it; switch it on and it works
Clients — Staff keep editing clients as before, and can now open Check-In; a Super Admin can switch either off
Clearer refusals — when something isn't allowed, the message names who to ask: an Admin or Super Admin
No buttons that can't work — a role without the switch no longer sees controls it can't use