Add settings management and UI configuration

- Implemented a SettingsManager class to handle application settings.
- Added a SettingsDialog for user configuration of various settings categories.
- Integrated settings loading and saving functionality with JSON.
- Created UI elements for general, editor, assistant, terminal, interface, shortcuts, and advanced settings.
- Applied settings to the Claude AI widget and editor upon initialization and when settings change.
- Enhanced the main application to restore window geometry and state on startup.
- Added functionality to apply themes and font settings across the application.

Author: André Machado