[CI Failure] SqlServerContainerFixture InitializeAsync fails because Ryuk image pull from netaspireci.azurecr.io is refused (connection refused)

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/34882504789
Build error leg: Tests / No-package tests (regular, Aspire.Hosting.Azure.Tests, Hosting.Azure, Hosting.Azure, tests/Aspire... / Hosting.Azure (ubuntu-latest)
Pull request: #19939

## Classification Analysis

All 7 failing tests fail identically in SqlServerContainerFixture.InitializeAsync while pulling the Testcontainers Ryuk image from netaspireci.azurecr.io, with a raw TCP connection refused error. This is an external container registry network issue unrelated to the PR, which does not touch Aspire.Hosting.Azure.Tests.

## Failure Information

Job output snippet

Class fixture type 'Aspire.Hosting.Azure.Tests.SqlServerContainerFixture' threw in InitializeAsync

---- Docker.DotNet.DockerApiException : Docker API responded with status code=InternalServerError, response={"message":"Head \"https://netaspireci.azurecr.io/v2/testcontainers/ryuk/manifests/0.14.0\": dial tcp 20.150.241.5:443: connect: connection refused"}

----- Inner Stack Trace -----

   at Docker.DotNet.DockerClient.HandleIfErrorResponseAsync(HttpStatusCode statusCode, HttpResponseMessage response) in /_/src/Docker.DotNet/DockerClient.cs:line 516

   at Docker.DotNet.DockerClient.MakeRequestForRawResponseAsync(HttpMethod method, String path, IQueryString queryString, IRequestContent body, IDictionary`2 headers, CancellationToken token) in /_/src/Docker.DotNet/DockerClient.cs:line 331

   at Docker.DotNet.Models.StreamUtil.MonitorResponseForMessagesAsync[T](Task`1 responseTask, DockerClient client, CancellationToken cancel, IProgress`1 progress) in /_/src/Docker.DotNet/Endpoints/StreamUtil.cs:line 80

   at DotNet.Testcontainers.Clients.DockerImageOperations.CreateAsync(IImage image, IDockerRegistryAuthenticationConfiguration dockerRegistryAuthConfig, CancellationToken ct) in /_/src/Testcontainers/Clients/DockerImageOperations.cs:line 73

   at DotNet.Testcontainers.Clients.TestcontainersClient.PullImageAsync(IImage image, CancellationToken ct) in /_/src/Testcontainers/Clients/TestcontainersClient.cs:line 430

   at DotNet.Testcontainers.Clients.TestcontainersClient.RunAsync(IContainerConfiguration configuration, CancellationToken ct) in /_/src/Testcontainers/Clients/TestcontainersClient.cs:line 337

   at DotNet.Testcontainers.Containers.DockerContainer.UnsafeCreateAsync(CancellationToken ct) in /_/src/Testcontainers/Containers/DockerContainer.cs:line 493

   at DotNet.Testcontainers.Containers.DockerContainer.StartAsync(CancellationToken ct) in /_/src/Testcontainers/Containers/DockerContainer.cs:line 337

   at DotNet.Testcontainers.Containers.ResourceReaper.GetAndStartNewAsync(...) in /_/src/Testcontainers/Containers/ResourceReaper.cs:line 231

## Description

SqlServerContainerFixture InitializeAsync fails because Ryuk image pull from netaspireci.azurecr.io is refused (connection refused)

**Type**: infra-failure

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-09-14 | [34882504789](https://github.com/microsoft/aspire/actions/runs/34882504789) | Tests / No-package tests (regular, Aspire.Hosting.Azure.Tests, Hosting.Azure, Hosting.Azure, tests/Aspire... / Hosting.Azure (ubuntu-latest) | #19939 |

Start with the reported CI job and the SqlServerContainerFixture.InitializeAsync failure; the issue attributes it to a refused connection while pulling Testcontainers' Ryuk image from netaspireci.azurecr.io. Check whether the registry failure is reproducible and whether the fixture or CI configuration needs attention. Done means the test job can initialize the fixture without that pull failure.

Written by the indexing model from the issue text.