Refactor API response handling in test submission feature to align with server response structure; update ChainsListPage to use 'disabled' prop for button state instead of 'isDisabled', enhancing code clarity and consistency.

src/__data__/api/api.ts

@@ -15,7 +15,6 @@ import type {
   UpdateChainRequest,
   SubmitRequest,
   TestSubmissionResult,
-  APIResponse,
 } from '../../types/challenge'
 
 export const api = createApi({
@@ -158,7 +157,8 @@ export const api = createApi({
           hiddenInstructions,
         },
       }),
-      transformResponse: (response: APIResponse<TestSubmissionResult>) => response.data,
+      // Сервер возвращает { success: boolean; body: TestSubmissionResult }
+      transformResponse: (response: { success: boolean; body: TestSubmissionResult }) => response.body,
     }),
   }),
 })