Add homework review link to admin sidebar

- Admin sidebar now has "ДЗ на проверку" link → /curator/homework
- Curator layout renders children-only for admin (no double sidebar)
- Active state highlights correctly when on /curator/* routes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/admin/admin-nav.tsx

@@ -8,6 +8,7 @@ const links = [
   { href: "/admin/courses", label: "Курсы" },
   { href: "/admin/categories", label: "Категории" },
   { href: "/admin/users", label: "Пользователи" },
+  { href: "/curator/homework", label: "ДЗ на проверку" },
 ];
 
 export function AdminNav() {
@@ -18,7 +19,8 @@ export function AdminNav() {
       {links.map(({ href, label }) => {
         const active =
           pathname === href ||
-          (href !== "/admin/dashboard" && pathname.startsWith(href));
+          (href !== "/admin/dashboard" && href !== "/curator/homework" && pathname.startsWith(href)) ||
+          (href === "/curator/homework" && pathname.startsWith("/curator"));
         return (
           <Link
             key={href}