Implement sort dart imports pre-commit hook

TODOS:

- [x] implement import_sorter with build tools ([commit](https://github.com/fusion44/blitz_gui/commit/6bd73cf500006f6c94f3c84a7a286cd715bf09fb))
- [x] sort imports
- [ ] implement pre-commit hook

https://pub.dev/packages/import_sorter

Start with the existing import_sorter build-tools setup referenced in the completed checklist and read the import_sorter package documentation. Add the repository's pre-commit integration so imports are checked or sorted automatically, then verify that the hook runs successfully on the project.

Written by the indexing model from the issue text.