feat: user preview, bulk and record actions and the permanent delete

- the list opens the preview, which shows one status hint (banned,
  deactivated, not activated, suspended) and the IP address fields
- bulk actions activate, deactivate, restore, ban and unban; record
  actions activate, unban and unsuspend, offered while they apply
- delete (form button and bulk) removes the user for good with the
  throttle rows, group memberships and attachments in one transaction;
  blobs go after the commit
- a privileged-group member is still refused, a bulk delete as a whole

controllers/admin_registry.go

@@ -25,4 +25,8 @@ func init() {
 	var _ pact.FilterOptions = usersAdminController{}
 	var _ pact.FormBeforeUpdate = usersAdminController{}
 	var _ pact.FormBeforeDelete = usersAdminController{}
+	var _ pact.FormAfterDelete = usersAdminController{}
+	var _ pact.HasAdminBulkActions = usersAdminController{}
+	var _ pact.HasAdminRecordActions = usersAdminController{}
+	var _ pact.AdminPartialData = usersAdminController{}
 }