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.

docs/modules/notify/resources/samples/airgap-time-drift@1.sample.json

@@ -0,0 +1,26 @@
+{
+  "eventId": "5cf2d3b2-9b90-4f7d-9a9a-54b8b5a5e3aa",
+  "kind": "airgap.time.drift",
+  "version": "1",
+  "tenant": "tenant-01",
+  "ts": "2025-10-31T06:15:00+00:00",
+  "actor": "airgap-time",
+  "payload": {
+    "anchorId": "anchor-2025-10-28",
+    "anchorIssuedAt": "2025-10-28T05:00:00Z",
+    "budgetSeconds": 259200,
+    "driftSeconds": 216000,
+    "links": {
+      "docs": "https://docs.stella-ops.org/airgap/staleness-and-time.html"
+    },
+    "nextAnchorDueBy": "2025-11-01T05:00:00Z",
+    "remainingSeconds": 43200,
+    "remediation": "Import the latest mirror bundle to refresh the time anchor or extend the budget via policy override before sealed mode blocks scheduled jobs.",
+    "severity": "high",
+    "status": "critical"
+  },
+  "attributes": {
+    "category": "airgap",
+    "anchorBudgetHours": "72"
+  }
+}