- Introduced `ThemeManager` to handle application themes using `ttkthemes`.
- Added `SettingsWindow` for user preferences including theme selection and UI settings.
- Integrated theme selection into the main application with a menu for quick access.
- Enhanced UI components with custom styles based on the selected theme.
- Implemented tooltips for better user guidance across various UI elements.
- Updated dependencies to include `ttkthemes` for improved visual appeal.
- Deleted `TESTING_SETUP.md` and `TEST_UPDATES_SUMMARY.md` as they were outdated.
- Introduced `CHANGELOG.md` to document notable changes and version history.
- Added `DEVELOPMENT.md` for detailed development setup, testing framework, and debugging guidance.
- Created `FEATURES.md` to outline core features and functionalities of TheChart.
- Established `README.md` as a centralized documentation index for users and developers.
