* chore: migrate to vitest
* test: speed up some suites by sharing sessions and mocking expensive non-tested actions
* test: refactor some tests to verify behavior instead of implementation details
* chore: fix linting issues
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
* **New Features**
* New CLI command to change user email addresses with impact preview and validation.
* **Accessibility**
* Improved settings form with proper label-input associations and email field type validation.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->