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-bundle-import@1.sample.json

@@ -0,0 +1,29 @@
+{
+  "eventId": "99b40f9c-4a34-4a5f-9e1a-0c1e5a97c0bb",
+  "kind": "airgap.bundle.import",
+  "version": "1",
+  "tenant": "tenant-01",
+  "ts": "2025-10-30T22:05:18+00:00",
+  "actor": "airgap-importer",
+  "payload": {
+    "bundleId": "mirror-2025-10-30",
+    "importedAt": "2025-10-30T22:02:03Z",
+    "links": {
+      "audit": "https://authority.airgap.local/authority/audit/airgap/entries/mirror-2025-10-30",
+      "docs": "https://docs.stella-ops.org/airgap/airgap-mode.html#import"
+    },
+    "remediation": "Review bundle warnings and plan the next mirror export to keep advisories within the allowed freshness budget.",
+    "severity": "medium",
+    "status": "completed",
+    "warnings": [
+      {
+        "code": "feeds.outdated",
+        "message": "OSV feed is 2 days old; schedule next mirror export sooner."
+      }
+    ]
+  },
+  "attributes": {
+    "importer": "ops:olivia",
+    "category": "airgap"
+  }
+}