Ensure the Basic Style Respects the Dark Mode

The current implementation of the Basic style does not support Dark mode. This task involves updating the Basic style to ensure compatibility with Dark mode and adherence to the system theme settings.

With the increasing adoption of Dark mode across applications and operating systems, users expect seamless transitions between light and dark themes. Supporting Dark mode improves user experience, accessibility, and aligns with modern UI standards. Also the Basic style is the default style if the current quick style does not implement the control.

Requirements

• Implement Dark mode support for the Basic style.
• Ensure proper adherence to the system theme settings (e.g., auto-switching based on system preference).
• Maintain accessibility standards, including sufficient color contrast and readability.

Subtasks

• Technical implementation
• Auto tests
• Update examples

TODO (✅⬜⌛)

✅ General colors for Dark mode
✅ Dynamic system theme update
⬜ CheckBox: Pressed+Hovered background color
⬜ ComboBox: background color of Hovered item
⬜ RadioButton: Pressed+Hovered background color
⬜ RangeSlider: brighter border color
⬜ Slider: same as RangeSlider
⬜ Tumbler: the further numbers are too much vague
✅ Update Gallery Controls example: enable Basic style settings

 ❌ Update QQuickBasicStyle class. (The style is not used)