The POST Delete(UnregisterViewModel) action and the GET Delete() action
both existed in AccountController, but Views/Account/Delete.cshtml was
missing — so GET /Account/Delete had no page to render. Add the
confirmation view (posts back to Delete with the user's UserId, with a
"Confirmer la suppression" button and an "Annuler" cancel link).
Add a smoke test: an authenticated GET /Account/Delete returns 200 and
the confirmation page body.
Co-Authored-By: Claude Code <noreply@anthropic.com>
