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/change_password.html

@@ -13,9 +13,9 @@
             Смените пароль, если хотите. После сохранения вы останетесь в системе.
         </p>
         <form class="card form-card form-stack" th:action="@{/change-password}" method="post">
-            <div><label class="label" for="old">Текущий пароль</label><input class="input" id="old" name="old" type="password" required></div>
-            <div><label class="label" for="new">Новый пароль</label><input class="input" id="new" name="new" type="password" required><p class="hint">Минимум 8 символов.</p></div>
-            <div><label class="label" for="new2">Повторите новый пароль</label><input class="input" id="new2" name="new2" type="password" required></div>
+            <div><label class="label" for="old">Текущий пароль</label><input class="input" id="old" name="old" type="password" autocomplete="current-password" required></div>
+            <div><label class="label" for="new">Новый пароль</label><input class="input" id="new" name="new" type="password" autocomplete="new-password" required><p class="hint">Минимум 8 символов.</p></div>
+            <div><label class="label" for="new2">Повторите новый пароль</label><input class="input" id="new2" name="new2" type="password" autocomplete="new-password" required></div>
             <button class="btn btn-primary" type="submit">Сменить пароль</button>
             <a th:if="${currentUser != null and !currentUser.mustChangePassword}"
                class="btn btn-secondary" th:href="${currentUser.admin} ? @{/admin} : @{/student}">Отмена</a>