GraphQL client Apollo implementation

Implement GraphQL with Apollo Client. Setup: 1. ApolloProvider with InMemoryCache. 2. useQuery hook for data fetching. 3. useMutation for data updates. 4. Optimistic UI responses. 5. Cache policies (cache-first, network-only). 6. Fragment composition for reusable fields. 7. Pagination with fetchMore. 8. Local state management. Use codegen for TypeScript types and implement error handling with Error Link.