Lab editing and group grades

- academic-service: PUT /labs/{id} (title, deadline, defense, points, status,
  description), POST/PUT/DELETE variants endpoints
- progress-service: lab_grades table, POST/GET /api/v1/grades, GET /me/grades
- gateway: routes for /api/v1/assign and /api/v1/grades
- web: lab edit page (metadata + per-variant forms + add/delete variant)
- web: group page shows grades matrix per lab with editable score inputs
  and computed average column
- web: student dashboard renders statement via markdown, shows deadline

web/src/main/resources/templates/admin/lab.html

@@ -10,6 +10,7 @@
             <p class="text-sm text-muted">Статус: <span class="badge" th:classappend="${lab.status == 'published'} ? 'badge-ok' : 'badge-warn'" th:text="${lab.status}">—</span></p>
         </div>
         <div class="flex gap-2">
+            <a class="btn btn-secondary" th:href="@{/admin/labs/{id}/edit(id=${lab.id})}">Редактировать</a>
             <form th:action="@{/admin/labs/{id}/distribute(id=${lab.id})}" method="post">
                 <button class="btn btn-primary" type="submit" name="force" value="false">Распределить</button>
             </form>