Modernize to .NET 8 MAUI with updated dependencies and breaking API fixes

[Copilot]

Rename the sample/test application project from ColorPickerTest to ColorPickerTestApp for clarity.

Changes

Project Structure

• Directory: ColorPickerTest/ → ColorPickerTestApp/
• Project file: ColorPickerTest.csproj → ColorPickerTestApp.csproj
• Solution file: Updated project name and path references

Code Updates

• All C# namespaces: ColorPickerTest → ColorPickerTestApp (17 files)
• All XAML x:Class and namespace declarations (3 files)
• Project properties: RootNamespace, ApplicationTitle

Documentation & CI

• README.md: Updated sample app references
• GitHub Actions workflow: Updated build paths for Android and Windows jobs

Original prompt

Repository: vpapenko/ColorPicker.Maui (repo id 465591797)
Default branch: main

Goal

• Modernize the repository to current .NET 8 MAUI.
• Fix outdated/broken dependencies.
• Ensure the solution builds successfully.
• Ensure a basic sample runs (at minimum: a sample app that launches and shows the color picker UI or a placeholder page demonstrating that the control loads and can change a bound Color).

Scope for this PR

1. Update target frameworks to .NET 8 MAUI (net8.0-android, net8.0-ios, net8.0-maccatalyst, net8.0-windows10.0.19041.0 as appropriate).
2. Update NuGet packages to versions compatible with .NET 8 MAUI.
3. Resolve compilation errors and API breaks due to MAUI/.NET updates.
4. Make sure a sample app (if present) builds and runs; if no sample exists, create a minimal MAUI sample project in the repo that references the library/control and demonstrates it.
5. Update README with build/run instructions for .NET 8.
6. Add/adjust GitHub Actions CI to build the solution on .NET 8 (at least Windows build; optionally Android build if feasible).

Acceptance criteria

• dotnet build succeeds on a clean environment with .NET 8 SDK installed.
• If a sample app exists/created, it can be launched (documented steps) and displays a page with the color picker control wired to a Color bindable property.
• Dependencies are updated and no deprecated/unsupported packages remain (or are documented if unavoidable).
• README documents prerequisites and how to run the sample.

Notes

• Keep changes focused on modernization/build/run; avoid adding new features beyond what is necessary to demonstrate the control works.
• If multiple projects exist (library + sample), ensure correct references and packaging metadata are not broken.

This pull request was created from Copilot chat.

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