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/Findings/StellaOps.Findings.Ledger/Hashing/LedgerHashing.cs

@@ -0,0 +1,20 @@
+using System.Text.Json.Nodes;
+
+namespace StellaOps.Findings.Ledger.Hashing;
+
+public static class LedgerHashing
+{
+    public static LedgerHashResult ComputeHashes(JsonObject canonicalEnvelope, long sequenceNumber)
+    {
+        var canonicalJson = LedgerCanonicalJsonSerializer.Serialize(canonicalEnvelope);
+        var eventHash = HashUtilities.ComputeSha256Hex(canonicalJson);
+        var merkleLeafInput = $"{eventHash}-{sequenceNumber}";
+        var merkleLeafHash = HashUtilities.ComputeSha256Hex(merkleLeafInput);
+        return new LedgerHashResult(eventHash, merkleLeafHash, canonicalJson);
+    }
+}
+
+public sealed record LedgerHashResult(
+    string EventHash,
+    string MerkleLeafHash,
+    string CanonicalJson);