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.

bench/reachability-benchmark/cases/py/unsafe-exec/case.yaml

@@ -0,0 +1,38 @@
+id: "py-unsafe-exec:101"
+language: py
+project: unsafe-exec
+version: "1.0.0"
+description: "Python handler with reachable eval sink"
+entrypoints:
+  - "POST /api/exec"
+sinks:
+  - id: "PyUnsafeExec::handle_request"
+    path: "src/app.py::handle_request"
+    kind: "process"
+    location:
+      file: src/app.py
+      line: 8
+    notes: "eval on user input"
+environment:
+  os_image: "python:3.12-alpine"
+  runtime:
+    python: "3.12"
+  source_date_epoch: 1730000000
+build:
+  command: "./build/build.sh"
+  source_date_epoch: 1730000000
+  outputs:
+    artifact_path: outputs/binary.tar.gz
+    sbom_path: outputs/sbom.cdx.json
+    coverage_path: outputs/coverage.json
+    traces_dir: outputs/traces
+test:
+  command: "./tests/run-tests.sh"
+  expected_coverage:
+    - outputs/coverage.json
+  expected_traces:
+    - outputs/traces/traces.json
+ground_truth:
+  summary: "Eval reachable via POST /api/exec"
+  evidence_files:
+    - "../benchmark/truth/py-unsafe-exec.json"