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/static/js/tablekit.js

@@ -158,13 +158,26 @@
             if (th.hasAttribute('data-nosort')) return;
             th.classList.add('th-sortable');
             if (!th.title) th.title = 'Сортировать по этому столбцу';
-            th.addEventListener('click', function (event) {
-                if (event.target.closest('form, button, a, select, input')) return;
+            // сортировка с клавиатуры: фокус + Enter/пробел, состояние доступно скринридеру
+            th.tabIndex = 0;
+            if (th.classList.contains('is-asc')) th.setAttribute('aria-sort', 'ascending');
+            function doSort() {
                 var asc = !th.classList.contains('is-asc');
                 clearAllMarkers(table);
                 th.classList.add(asc ? 'is-asc' : 'is-desc');
+                th.setAttribute('aria-sort', asc ? 'ascending' : 'descending');
                 sortColumn(table, index, asc ? 1 : -1);
                 th.title = (th.textContent.trim() || 'Столбец') + ' — ' + (asc ? 'по возрастанию' : 'по убыванию');
+            }
+            th.addEventListener('click', function (event) {
+                if (event.target.closest('form, button, a, select, input')) return;
+                doSort();
+            });
+            th.addEventListener('keydown', function (event) {
+                if (event.target !== th) return;
+                if (event.key !== 'Enter' && event.key !== ' ') return;
+                event.preventDefault();
+                doSort();
             });
         });
         buildFilters(table);