feat: add tickets tab to admin user detail page

Add ability to view user's tickets directly from the user detail page.
Backend gets user_id filter on tickets endpoint, frontend shows ticket
list with status badges, message preview and navigation to ticket.

src/api/admin.ts

@@ -101,6 +101,7 @@ export const adminApi = {
       per_page?: number;
       status?: string;
       priority?: string;
+      user_id?: number;
     } = {},
   ): Promise<AdminTicketListResponse> => {
     const response = await apiClient.get('/cabinet/admin/tickets', { params });