The language website ran a Spring Boot application on JVM 25 for two
endpoints, and it was the only JVM on the server: a quarter of a
gigabyte of resident memory for /api/v1/site and /health. The server
already runs ASP.NET Core 10 for Progmaweb.

The API is now Progmasoft.Tala.Website.Api, a minimal ASP.NET Core 10
application under the namespace Progmasoft.Tala.Website. It answers as
before: /api/v1/site returns the site's own state as the same JSON,
POST is not allowed there, /health answers with an empty 200, and every
other path is 404. It listens on 127.0.0.1, port 5086 unless PORT says
otherwise, as the Spring process did, so Nginx is unchanged.

- Progmasoft.Tala.Website.slnx, Directory.Build.props and global.json
  set up the solution with warnings as errors, documentation comments
  required and NuGet lock files.
- Progmasoft.Tala.Website.Api.Tests runs the endpoints in an in-memory
  host with xUnit v3 on Microsoft.Testing.Platform.
- ops/systemd/tala-site-api.service runs the published DLL on the shared
  runtime from /srv/xsharp/website/current/site-api, with the hardening
  of the unit it replaces.
- CI builds, tests, publishes and reports coverage with dotnet; CodeQL
  analyzes C# instead of Kotlin; Renovate watches NuGet instead of
  Gradle.

The pages were renamed; the rest of the repository still said Visual X#:
- the site API answered with the name Visual X#, and its test expected it;
- the documents, the issue and pull request templates, the support address
  and the name of the code scanning configuration.

The documents also said that a left-to-right mark follows the name of the
language in Hebrew text. That was for the `#` of the old name; the sentence
now speaks of names that end in a symbol, such as C#.

Not changed: host names, paths and unit names on the server, the name of the
backend artifact, the Kotlin package of the backend, and the keys of the
browser storage.