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/Graph/StellaOps.Graph.Indexer/Schema/Base32Crockford.cs

@@ -0,0 +1,44 @@
+using System.Text;
+
+namespace StellaOps.Graph.Indexer.Schema;
+
+/// <summary>
+/// Base32 encoder using the Crockford alphabet (0-9A-HJKMNPQRSTVWXYZ).
+/// </summary>
+internal static class Base32Crockford
+{
+    private const string Alphabet = "0123456789ABCDEFGHJKMNPQRSTVWXYZ";
+
+    public static string Encode(ReadOnlySpan<byte> data)
+    {
+        if (data.IsEmpty)
+        {
+            return string.Empty;
+        }
+
+        var output = new StringBuilder((data.Length * 8 + 4) / 5);
+        var buffer = 0;
+        var bitsLeft = 0;
+
+        foreach (var b in data)
+        {
+            buffer = (buffer << 8) | b;
+            bitsLeft += 8;
+
+            while (bitsLeft >= 5)
+            {
+                bitsLeft -= 5;
+                var index = (buffer >> bitsLeft) & 0x1F;
+                output.Append(Alphabet[index]);
+            }
+        }
+
+        if (bitsLeft > 0)
+        {
+            var index = (buffer << (5 - bitsLeft)) & 0x1F;
+            output.Append(Alphabet[index]);
+        }
+
+        return output.ToString();
+    }
+}