Add TypedClient sample apps and fix client naming and Asp.Versioning imports

[davidkallesen]

Fixes two TypedClient generation defects and adds runnable console apps that
demonstrate how to consume the generated clients.

Generator fixes:

• Client class naming
  The generated client type name was derived from the full project name, so a
  dotted name such as "Eloverblik.Api.ThirdPartyApi" produced an invalid
  identifier. HttpClientExtractor and ApiClientGenerator now use
  CasingHelper.GetLastNameSegment(projectName), yielding "ThirdPartyApiClient".

• Asp.Versioning using import
  UsingStatementHelper matched the bare "ApiVersion" token, so ordinary
  client-side member access such as "parameters.ApiVersion" pulled in the
  server-only Asp.Versioning namespace and broke the build. The mapping now
  keys on the construction shape "new ApiVersion(" instead.

Both fixes are covered by new tests in HttpClientExtractorTests and
UsingStatementHelperTests.

Samples:

• Restructured the ThirdParty-EPO-Clients and ThridParty-Typed-Clients folders
  and added the EloverblikThirdPartyApiClient TypedClient sample.
• Added EloverblikThirdPartyApiClient-App console apps for both generation
  modes, showing host setup, IHttpClientFactory registration and the generated
  API surface. Authentication is handled by a BearerTokenProvider singleton
  read by a BearerTokenHandler on each request, since IHttpClientFactory pools
  handlers and Eloverblik exchanges a refresh token for a short-lived access
  token mid-session.
• The paired apps make the mode differences explicit: EndpointPerOperation
  resolves per-operation endpoint interfaces from DI via the generated
  AddEloverblikApiThirdPartyApiEndpoints() and returns result wrappers with
  IsOk/IsUnauthorized branches, while TypedClient registers a single
  ThirdPartyApiClient typed client whose methods return payloads directly and
  throw HttpRequestException on non-success.
• Both apps registered in Atc.Rest.Api.SourceGenerator.slnx.