refactor: optimize memory usage and clean up codebase

- Remove unnecessary test files and move to project root
- Optimize useMaterializeInput with shallowRef for large data
- Add proper cleanup in onUnmounted hooks
- Use toRaw() in PivotData creation to reduce reactivity overhead
- Remove unused usePivotModelHistory and useDraggableMemoryFix
- Simplify main.ts to use App.vue directly
- Remove deep watch to prevent performance issues

Author: Seungwoo321