Regression: Button is nearly invisible in Dark Mode when VisualStyleMode = Classic

[Olina-Zhang]

.NET version

.NET 11.0.100-preview.7.26365.114 + Private dlls built from Net11/Integration-2 branch of https://github.com/KlausLoeffelmann/winforms repo

Did it work in .NET Framework?

Yes

Did it work in any of the earlier releases of .NET Core or .NET 5+?

Not support, new feature

Issue description

After the introduction of VisualStyleMode, Button controls are rendered incorrectly in Dark Mode when the Form's VisualStyleMode is set to Classic. Not repro in VisualStyleMode = NET11

The button blends into the background because both the button surface and its text are rendered with very low contrast, making the control difficult to recognize and use.

Steps to reproduce

1. Create a WinForms application targeting .NET 11.
2. Set the Form's VisualStyleMode to Classic.
3. Add a Button to the Form.
4. Enable the DarkMode in program.cs:
   Application.SetColorMode(SystemColorMode.Dark);
5. Run the application to observe.

[Olina-Zhang]

@KlausLoeffelmann tested the fix in .NET 11/Integration-3, the button is now visible, but the focus indicator (should with white color, not black color) is not visible when using the Tab key to switch focus. The focusing button border doesn't seem very prominent either. Below are the results compared to .NET 10.