Add unit tests for SBOM ingestion and transformation

- Implement `SbomIngestServiceCollectionExtensionsTests` to verify the SBOM ingestion pipeline exports snapshots correctly.
- Create `SbomIngestTransformerTests` to ensure the transformation produces expected nodes and edges, including deduplication of license nodes and normalization of timestamps.
- Add `SbomSnapshotExporterTests` to test the export functionality for manifest, adjacency, nodes, and edges.
- Introduce `VexOverlayTransformerTests` to validate the transformation of VEX nodes and edges.
- Set up project file for the test project with necessary dependencies and configurations.
- Include JSON fixture files for testing purposes.

src/Cli/StellaOps.Cli/Commands/CommandHandlers.cs

@@ -354,7 +354,7 @@ internal static class CommandHandlers
                 throw new InvalidOperationException("Tenant must be provided via --tenant or STELLA_TENANT.");
             }
 
-            var payload = await LoadIngestInputAsync(input, cancellationToken).ConfigureAwait(false);
+            var payload = await LoadIngestInputAsync(services, input, cancellationToken).ConfigureAwait(false);
 
             logger.LogInformation("Executing ingestion dry-run for source {Source} using input {Input}.", source, payload.Name);
 
@@ -5009,22 +5009,22 @@ internal static class CommandHandlers
         return string.IsNullOrWhiteSpace(fromEnvironment) ? string.Empty : fromEnvironment.Trim();
     }
 
-    private static async Task<IngestInputPayload> LoadIngestInputAsync(string input, CancellationToken cancellationToken)
+    private static async Task<IngestInputPayload> LoadIngestInputAsync(IServiceProvider services, string input, CancellationToken cancellationToken)
     {
         if (Uri.TryCreate(input, UriKind.Absolute, out var uri) &&
             (uri.Scheme.Equals(Uri.UriSchemeHttp, StringComparison.OrdinalIgnoreCase) ||
              uri.Scheme.Equals(Uri.UriSchemeHttps, StringComparison.OrdinalIgnoreCase)))
         {
-            return await LoadIngestInputFromHttpAsync(uri, cancellationToken).ConfigureAwait(false);
+            return await LoadIngestInputFromHttpAsync(services, uri, cancellationToken).ConfigureAwait(false);
         }
 
         return await LoadIngestInputFromFileAsync(input, cancellationToken).ConfigureAwait(false);
     }
 
-    private static async Task<IngestInputPayload> LoadIngestInputFromHttpAsync(Uri uri, CancellationToken cancellationToken)
+    private static async Task<IngestInputPayload> LoadIngestInputFromHttpAsync(IServiceProvider services, Uri uri, CancellationToken cancellationToken)
     {
-        using var handler = new HttpClientHandler { AutomaticDecompression = DecompressionMethods.All };
-        using var httpClient = new HttpClient(handler);
+        var httpClientFactory = services.GetRequiredService<IHttpClientFactory>();
+        var httpClient = httpClientFactory.CreateClient("stellaops-cli.ingest-download");
         using var response = await httpClient.GetAsync(uri, cancellationToken).ConfigureAwait(false);
 
         if (!response.IsSuccessStatusCode)