feat: Add projection showcase sample

[MartinZikmund]

GitHub Issue: closes #

PR Type: ✨ Feature

What is the current behavior? 🤔

What is the new behavior? 🚀

PR Checklist ✅

Please check if your PR fulfills the following requirements:

• 📝 Commits must be following the Conventional Commits specification.
• 🧪 Added Runtime tests, UI tests, or a manual test sample for the changes have been added (for bug fixes / features) (if applicable)
• 📚 Docs have been added/updated which fit documentation template (for bug fixes / features)
• 🖼️ Validated PR Screenshots Compare Test Run results.
• ❗ Contains NO breaking changes

Other information ℹ️

[Copilot]

Pull request overview

This PR adds a new sample project called "Projection Showcase" to the Uno.Samples repository. The sample demonstrates 3D projection and animation capabilities in Uno Platform using PlaneProjection and Matrix3DProjection classes. It includes five animated scenes (Orbiting Cards, Floating Tiles, Flip Card, Perspective Tunnel, and Matrix3D Wave) that showcase rotation, depth, and perspective effects driven by a DispatcherTimer at 60 FPS.

Changes:

• Added new ProjectionShowcase sample project with complete Uno Platform multi-target configuration
• Added documentation entry in doc/samples.md describing the new sample
• Included README.md and sample screenshot demonstrating the projection effects

Reviewed changes

Copilot reviewed 52 out of 56 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
doc/samples.md	Added entry for Projection Showcase sample with description and source link
UI/ProjectionShowcase/README.md	Sample documentation with overview, codebase description, and Uno Platform information
UI/ProjectionShowcase/src/ProjectionShowcase/MainPage.xaml	XAML layout defining five animation sections using PlaneProjection and Matrix3DProjection
UI/ProjectionShowcase/src/ProjectionShowcase/MainPage.xaml.cs	C# code-behind implementing animation logic with DispatcherTimer
UI/ProjectionShowcase/src/ProjectionShowcase/App.xaml.cs	Standard Uno Platform application initialization and logging setup
UI/ProjectionShowcase/src/ProjectionShowcase/ProjectionShowcase.csproj	Uno.Sdk project file targeting multiple platforms (Android, iOS, Windows, WebAssembly, Desktop)
UI/ProjectionShowcase/src/global.json	Uno.Sdk version configuration (6.4.42)
UI/ProjectionShowcase/docs/assets/sample.png	Screenshot demonstrating the sample's visual output
[Various platform-specific files]	Standard Uno Platform configuration files for Android, iOS, WebAssembly, Desktop, and Windows platforms

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[Copilot]

There is a typo in the description. "DispatcherTimer" should be "DispatcherTimer" (remove the backtick before the 'r').

[Copilot]

The ApplicationPublisher is set to "Martin", which appears to be a personal name. For consistency with other Uno Platform samples, consider using either "Uno Platform" (as seen in many samples like AutoSuggestSample, Benchmark, etc.) or the application name "ProjectionShowcase" (as seen in samples like EFCoreSQLiteSample, SkiaSharpTest, etc.).

[Copilot]

The PR description is incomplete. It's missing the following required information:

• "What is the current behavior?" section is empty
• "What is the new behavior?" section is empty
• PR checklist items are not checked

Please fill in these sections to describe what the PR adds (a new sample demonstrating 3D projection capabilities) and check the relevant boxes in the checklist.

[Copilot]

The array fields (_cards, _cardProjs, _tileProjs, _ringProjs, _waveProjs) are declared without initialization and are assigned in OnLoaded. Consider initializing them to avoid potential null reference warnings from the compiler, or add null-forgiving operators (!) when accessing them, or mark them with nullable reference types appropriately. For example:

private Border[] _cards = null!;
private PlaneProjection[] _cardProjs = null!;

This makes it explicit that these fields will be assigned before use.

Suggested change

	private Border[] _cards;
	private PlaneProjection[] _cardProjs;
	private PlaneProjection[] _tileProjs;
	private PlaneProjection[] _ringProjs;
	private Matrix3DProjection[] _waveProjs;
	private Border[] _cards = null!;
	private PlaneProjection[] _cardProjs = null!;
	private PlaneProjection[] _tileProjs = null!;
	private PlaneProjection[] _ringProjs = null!;
	private Matrix3DProjection[] _waveProjs = null!;

[Copilot]

The PR description is missing a proper GitHub issue reference. According to the Uno Platform contributing guidelines, every PR must reference a proper GitHub issue using one of these formats:

• Fixes https://github.com/unoplatform/<REPO>/issues/#<ISSUE_NUMBER>
• Closes https://github.com/unoplatform/<REPO>/issues/#<ISSUE_NUMBER>
• Related to https://github.com/unoplatform/<REPO>/issues/#<ISSUE_NUMBER>

The description currently shows "closes #" without an issue number. Please provide the associated issue number, or if no issue exists, add a note explaining why (e.g., "Note: No related issue (Internal maintenance / Approved by Team member: @username)").

[Copilot]

The web.config sets <customErrors mode="Off"/>, which causes ASP.NET to return full error details and stack traces to any client. An attacker can trigger server-side errors (for example, by requesting invalid or unexpected resources) and gain insights into file paths, configuration, and framework internals that facilitate further attacks. In production, configure customErrors to a safer value (such as RemoteOnly) and use a generic error page so detailed diagnostics are never exposed to external users.