Make the Application Examples Shipped with Qt Accessible on All Platforms with System Accessibility Support

Update three selected Qt application examples to demonstrate best practices for accessibility (a11y) on platforms that provide a system accessibility backend. This includes desktop platforms (e.g., Windows, macOS, Linux with a11y services) and mobile platforms (e.g., Android and iOS).

The examples should:

• Respect user appearance settings such as high contrast, theming, and font sizes

• Support proper keyboard and touch navigation

• Be fully accessible to screen readers

Platforms without a system accessibility backend (e.g., embedded Linux) are out of scope. The goal is to provide clear reference implementations that help developers create accessible Qt applications across supported platforms.