fix: Misc code quality improvements

[BenjaminMichaelis]

• Refactor path handling to use Path.Join for improved readabilitu

[Copilot]

Pull request overview

This PR refactors code for improved quality and readability, primarily replacing Path.Combine with Path.Join throughout the codebase and converting imperative loops to more idiomatic LINQ expressions. These changes align the codebase with modern .NET conventions and improve maintainability without altering functionality.

Changes:

• Replaced all instances of Path.Combine with Path.Join for path handling across web, test, and chat projects
• Refactored nested if-statements and foreach loops to use LINQ expressions for improved readability
• Simplified conditional logic using ternary operators where appropriate

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
EssentialCSharp.Web/Services/SiteMappingService.cs	Changed Path.Combine to Path.Join for sitemap.json path
EssentialCSharp.Web/Services/RouteConfigurationService.cs	Flattened nested if-statements into single conditional check
EssentialCSharp.Web/Helpers/SitemapXmlHelpers.cs	Changed Path.Combine to Path.Join for sitemap.xml path
EssentialCSharp.Web/Extensions/SiteMappingListExtensions.cs	Refactored foreach loop to LINQ Select/FirstOrDefault, fixing variable shadowing
EssentialCSharp.Web/Controllers/HomeController.cs	Changed Path.Combine to Path.Join in two locations, removing redundant nested Path.Combine
EssentialCSharp.Web/Areas/Identity/Pages/Account/Logout.cshtml.cs	Simplified if-else to ternary operator for return statement
EssentialCSharp.Web.Tests/WebApplicationFactory.cs	Changed Path.Combine to Path.Join for TestData path
EssentialCSharp.Web.Tests/ListingSourceCodeServiceTests.cs	Changed Path.Combine to Path.Join for TestData path
EssentialCSharp.Chat/Program.cs	Changed Path.Combine to Path.Join for output file path
EssentialCSharp.Chat.Shared/Services/ChunkingResultExtensions.cs	Refactored foreach loop to LINQ Select, added System.Linq using
EssentialCSharp.Chat.Shared/Services/AIChatService.cs	Refactored foreach loop to LINQ OfType/FirstOrDefault for cleaner code

[Copilot]

The using System.Linq; directive is redundant in .NET 6+ when ImplicitUsings is enabled (which is the default). System.Linq is automatically included in implicit usings. Consider removing this explicit using statement to align with modern .NET conventions.

Suggested change

using System.Linq;

[Copilot]

The comment indentation is incorrect. The comment should be aligned at the same level as the code it describes (the return statement), not indented further. Comments should maintain consistent indentation with the code they document.