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/users/_hint.htm

@@ -0,0 +1,7 @@
+{{- /* Status hint above the user preview: one callout, or nothing (usersHintView). */ -}}
+{{- if .Data.Title -}}
+<div class="summer-callout summer-callout--{{ .Data.Kind }}" role="status">
+<p class="summer-callout__title">{{ trans .Data.Title }}</p>
+<p class="summer-callout__text">{{ trans .Data.Text }}</p>
+</div>
+{{- end -}}