Redux Toolkit modern Redux patterns

Use Redux Toolkit for efficient Redux. APIs: 1. configureStore with defaults. 2. createSlice for reducers and actions. 3. Immer for immutable updates. 4. createAsyncThunk for async logic. 5. RTK Query for data fetching. 6. Entity adapter for normalized data. 7. TypeScript inference. 8. DevTools extension. No more action constants. Use createSelector for memoized selectors and implement listener middleware for side effects.