feat: register the Users admin screen with the privileged-member guard

- permissions (the four Winter codes and manage_privileged_groups),
  the user navigation item and the embedded admin YAML
- Users controller: list with deactivated users, row states, the
  groups, created date and activated filters, and the form's name,
  surname and email
- a member of a group in golem15.user.privileged_groups (default
  admin) keeps their email, password and row unless the administrator
  holds golem15.users.manage_privileged_groups; the refusal is a 403
  that saves nothing

models/user/columns.yaml

@@ -0,0 +1,28 @@
+columns:
+    id:
+        label: golem15.user::lang.user.id
+        invisible: true
+    name:
+        label: golem15.user::lang.user.name
+        searchable: true
+    surname:
+        label: golem15.user::lang.user.surname
+        searchable: true
+        invisible: true
+    email:
+        label: golem15.user::lang.user.email
+        searchable: true
+    created_at:
+        label: golem15.user::lang.user.created_at
+        type: datetime
+    last_seen:
+        label: golem15.user::lang.user.last_seen
+        type: datetime
+    created_ip_address:
+        label: golem15.user::lang.user.created_ip_address
+        searchable: true
+        invisible: true
+    last_ip_address:
+        label: golem15.user::lang.user.last_ip_address
+        searchable: true
+        invisible: true

models/user/fields.yaml

@@ -0,0 +1,16 @@
+fields:
+    name:
+        label: golem15.user::lang.user.name
+        type: text
+        span: left
+        tab: golem15.user::lang.user.account
+    surname:
+        label: golem15.user::lang.user.surname
+        type: text
+        span: right
+        tab: golem15.user::lang.user.account
+    email:
+        label: golem15.user::lang.user.email
+        type: text
+        span: full
+        tab: golem15.user::lang.user.account