Add file results documentation for Minimal APIs and controllers

[mikekistler]

Adds documentation for file result return values in ASP.NET Core, covering both Minimal APIs and controller-based APIs.

What's included

• File result types — TypedResults.File / ControllerBase.File() with byte[] and Stream
• OpenAPI support — Using Produces<Stream> for binary, Produces<string> for text
• Conditional requests — ETag and Last-Modified with 304 Not Modified
• Range requests — enableRangeProcessing for partial content (206) responses

Code examples reference snippets in dotnet/AspNetCore.Docs.Samples (PR: dotnet/AspNetCore.Docs.Samples#312).

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Internal previews

📄 File	🔗 Preview link
aspnetcore/fundamentals/minimal-apis/responses.md	How to create responses in Minimal API apps

[wadepickett]

Great content. I found a few minor items, with suggestions inline.

[wadepickett]

There is a build issue warning of missing code:
The article references code snippets at "~/../AspNetCore.Docs.Samples/fundamentals/minimal-apis/FileResults/10.x/

This will be resolved when the following PR is merged:
dotnet/AspNetCore.Docs.Samples#312

[wadepickett]

There is a build issue warning of missing code:
The article references code snippets at "~/../AspNetCore.Docs.Samples/fundamentals/minimal-apis/FileResults/10.x/

[wadepickett]

Closing and reopening to force new buld, now that samples on aspnetcore.docs.samples it links to from R dotnet/AspNetCore.Docs.Samples#312 has merged.

[wadepickett]

@mikekistler: Approved. Merging..