Admin group: single table, defense actions in cells; flash messages as toasts

web/src/main/resources/templates/setup.html

@@ -6,7 +6,6 @@
     <div class="container-sm">
         <h1 class="page-title">Создание администратора</h1>
         <p class="text-sm text-muted mb-4">Это разовая настройка. Аккаунт преподавателя создаётся один раз.</p>
-        <div th:if="${error}" class="alert alert-error" th:text="${error}"></div>
         <form class="card form-card form-stack" th:action="@{/setup}" method="post">
             <div><label class="label" for="login">Логин</label><input class="input" id="login" name="login" th:value="${login}" autofocus required></div>
             <div><label class="label" for="password">Пароль</label><input class="input" id="password" name="password" type="password" required><p class="hint">Минимум 8 символов.</p></div>