feat(graph): introduce graph.inspect.v1 contract and schema for SBOM relationships

- Added graph.inspect.v1 documentation outlining payload structure and determinism rules.
- Created JSON schema for graph.inspect.v1 to enforce payload validation.
- Defined mapping rules for graph relationships, advisories, and VEX statements.

feat(notifications): establish remediation blueprint for gaps NR1-NR10

- Documented requirements, evidence, and tests for Notifier runtime.
- Specified deliverables and next steps for addressing identified gaps.

docs(notifications): organize operations and schemas documentation

- Created README files for operations, schemas, and security notes to clarify deliverables and policies.

feat(advisory): implement PostgreSQL caching for Link-Not-Merge linksets

- Created database schema for advisory linkset cache.
- Developed repository for managing advisory linkset cache operations.
- Added tests to ensure correct functionality of the AdvisoryLinksetCacheRepository.

docs/notifications/schemas/README.md

@@ -0,0 +1,3 @@
+# Notify Schemas Catalog
+
+Placeholder for NR1 deliverables: versioned JSON Schemas for Notify event envelopes, rules, templates, channels, receipts, and webhooks. Publish `notify-schemas-catalog.json` + `.dsse.json` here with canonicalization recipe (BLAKE3-256 over normalized JSON) and `inputs.lock` capturing digests.