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.

seed-data/findings-ledger/fixtures/finding-projection.sample.json

@@ -0,0 +1,19 @@
+{
+  "currentEventId": "3ac1f4ef-3c26-4b0d-91d4-6a6d3a5bde10",
+  "cycleHash": "1a61c14efc1aceaed7d2574d2054475b2683a3bfc81103585070ef560b15bd02",
+  "explainRef": "explain://tenant-a/findings/3ac1f4ef",
+  "findingId": "artifact:sha256:3f1e2d9c7b1a0f6534d1b6f998d7a5c3ef9e0ab92f4c1d2e3f5a6b7c8d9e0f1a|pkg:cpe:/o:vendor:product",
+  "labels": {
+    "kev": true,
+    "runtime": "exposed"
+  },
+  "policyVersion": "sha256:5f38c7887d4a4bb887ce89c393c7a2e23e6e708fda310f9f3ff2a2a0b4dffbdf",
+  "severity": 6.7,
+  "status": "triaged",
+  "tenantId": "tenant-a",
+  "updatedAt": "2025-11-03T15:12:05.456Z",
+  "policyRationale": [
+    "explain://tenant-a/findings/3ac1f4ef",
+    "policy://tenant-a/policy-v1/rationale/accepted"
+  ]
+}