feat: Implement Filesystem and MongoDB provenance writers for PackRun execution context

- Added `FilesystemPackRunProvenanceWriter` to write provenance manifests to the filesystem.
- Introduced `MongoPackRunArtifactReader` to read artifacts from MongoDB.
- Created `MongoPackRunProvenanceWriter` to store provenance manifests in MongoDB.
- Developed unit tests for filesystem and MongoDB provenance writers.
- Established `ITimelineEventStore` and `ITimelineIngestionService` interfaces for timeline event handling.
- Implemented `TimelineIngestionService` to validate and persist timeline events with hashing.
- Created PostgreSQL schema and migration scripts for timeline indexing.
- Added dependency injection support for timeline indexer services.
- Developed tests for timeline ingestion and schema validation.

docs/modules/vuln-explorer/architecture.md

@@ -55,6 +55,7 @@ CLI mirrors these endpoints (`stella findings list|view|update|export`). Console
 - Logs: structured with `findingId`, `artifactId`, `advisory`, `policyVersion`, `actor`, `actionType`.
 - Audit exports: `audit_log.jsonl` appended whenever state changes; offline bundles include signed audit log and manifest.
 - Compliance: accepted risk requires dual approval and stores justification plus expiry reminders (raised through Notify).
+- Runbook and dashboard stub for demo snapshot: `runbooks/observability.md` and `runbooks/dashboards/vuln-explorer-observability.json` (offline import).
 
 ## 6) Identity & access integration