[6.5] Story: Update Scaffold Template

## Description

Update cgov-react-app-playground scaffold template to use shared library by default.

**Parent Issue:** #EPIC_6

### Sub-Tasks
- [ ] Add @nciocpl/react-app-shared to template dependencies
- [ ] Update example code to use shared components
- [ ] Remove duplicate atomic component folder
- [ ] Update scaffold documentation

### Notes
* New apps should use shared library from the start