Suggestions flyout menu color and word corrections

[Biyakuga Higashiri (Biyakuga)]

1. The visual styling of flyouts, popups, and suggestion surfaces throughout the application does not appear to match the default WinUI 3 / Windows 11 Fluent Design appearance.

For example, when comparing the application to the Windows Community Toolkit Gallery sample, flyout surfaces in the sample appear lighter (approximately #F9F9F9) and consistent with standard Windows 11 Fluent Design surfaces. In this application, equivalent flyouts appear noticeably darker and grayer (approximately #F3F3F3).
This behavior is not limited to the TokenizingTextBox suggestions flyout and appears to affect flyouts globally across the application.

2. Windows 11 displays text prediction, spelling correction, and word suggestion flyouts while typing in a specific input field within the application. These system-provided suggestions interfere with the intended user experience and overlap with application-provided suggestions.
   An example of this behavior can be seen in the attached TokenizingTextBox screenshot, where the Windows suggestion/spelling flyout is displayed while the control is also presenting its own suggestions.