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/admin/dashboard.html

@@ -19,7 +19,7 @@
         <div>
             <div class="flex items-center justify-between mb-4">
                 <h2 class="section-title">Лабораторные</h2>
-                <a th:href="@{/admin/labs}" class="text-sm">Все →</a>
+                <a th:href="@{/admin/labs}" class="text-sm">Все лабораторные →</a>
             </div>
             <div class="card card-flush">
                 <table>
@@ -36,7 +36,7 @@
         <div>
             <div class="flex items-center justify-between mb-4">
                 <h2 class="section-title">Группы</h2>
-                <a th:href="@{/admin/groups}" class="text-sm">Все →</a>
+                <a th:href="@{/admin/groups}" class="text-sm">Все группы →</a>
             </div>
             <div class="card card-flush">
                 <table>