Redesign B3 bordeaux + finish lab-page rework

- Lab page is now read-only with a settings screen for levels/variants;
  variant issuance moved to a large modal on the group page (assign-fragment).
- Header: bordeaux logo and 2px accent underline, bordeaux login/logout/theme
  buttons; smaller radii across the UI; filled secondary/danger buttons.
- Includes prior agent work (login backoff, no-cache pages, API timeouts,
  content tweaks) and fixes (variant usage Map.values, import order).
- Bump static asset version to v=9.

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

@@ -9,8 +9,8 @@
             Аккаунт администратора ещё не создан. <a th:href="@{/setup}">Создать первый аккаунт</a>
         </div>
         <form class="card form-card form-stack" th:action="@{/login}" method="post">
-            <div><label class="label" for="login">Логин</label><input class="input" id="login" name="login" th:value="${login}" autofocus required></div>
-            <div><label class="label" for="password">Пароль</label><input class="input" id="password" name="password" type="password" required></div>
+            <div><label class="label" for="login">Логин</label><input class="input" id="login" name="login" autocomplete="username" th:value="${login}" autofocus required></div>
+            <div><label class="label" for="password">Пароль</label><input class="input" id="password" name="password" type="password" autocomplete="current-password" required></div>
             <button class="btn btn-primary" type="submit">Войти</button>
         <input type="hidden" name="_csrf" th:value="${csrfToken}">
         </form>