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

admin_navigation.go

@@ -0,0 +1,31 @@
+package user
+
+import (
+	"git.golem15.com/golem15/sm-user-plugin/controllers"
+	"git.golem15.com/golem15/summercms/modules/pact"
+)
+
+// Navigation is the plugin's Winter registerNavigation() entry: the main item
+// user (order 555) with its side menu. Controller names an admin controller
+// id in place of a backend URL, and icons are lucide names.
+func (*Plugin) Navigation() []pact.NavigationItem {
+	return []pact.NavigationItem{
+		{
+			Code:        "user",
+			Label:       "golem15.user::lang.users.menu_label",
+			Icon:        "user",
+			Permissions: []string{"golem15.users.*"},
+			Order:       555,
+			Controller:  "golem15.user.users",
+			SideMenu: []pact.NavigationItem{
+				{
+					Code:        "users",
+					Label:       "golem15.user::lang.users.menu_label",
+					Icon:        "user",
+					Permissions: []string{controllers.PermissionAccessUsers},
+					Controller:  "golem15.user.users",
+				},
+			},
+		},
+	}
+}