refactor(graph): absorb Cartographer into graph-api + wire Graph Indexer

- Wire Graph Indexer library + Persistence into graph-api (csproj refs + DI)
- Add build/overlay endpoints matching Scheduler HTTP contracts
  (POST/GET /api/graphs/builds, POST/GET /api/graphs/overlays)
- Add PostgresGraphRepository for reading from graph.graph_nodes/edges
- Register SBOM ingest, analytics, change-stream, and inspector pipelines
- Comment out Cartographer container in compose (empty shell, Slot 21)
- Add cartographer.stella-ops.local as backwards-compat alias on graph-api
- Update Scheduler config to target graph.stella-ops.local
- Update services-matrix.env, hosts file, port-registry, module-matrix
- Update component-map, architecture docs, Scanner/Graph READMEs
- Eliminates 1 container (stellaops-cartographer)

All 133 existing tests pass (77 Api + 37 Indexer + 19 Core).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/technical/architecture/component-map.md

@@ -16,8 +16,8 @@ Concise descriptions of every top-level component under `src/`, summarising the
 - **SbomService** — SBOM inventory store and delta cache leveraged by Scanner, Policy Engine, Cartographer, and Export Center (`docs/modules/scanner/architecture.md`, SBOM sections). 
 - **RiskEngine** — Consolidates Policy verdicts, runtime signals, and graph overlays into prioritised risk views (`docs/modules/policy/architecture.md`, `docs/modules/graph/architecture.md`). 
 - **Findings** — Materialises effective findings from Policy Engine outputs and evidence. Feeds UI, CLI, Notify, and Governance dashboards (`docs/modules/policy/architecture.md`, findings sections). 
-- **Cartographer** — Builds identity graphs from SBOM/advisory data for Graph Explorer and RiskEngine (`docs/modules/graph/architecture.md`). 
-- **Graph** — Graph API + indexer, exposing relationship queries to UI/CLI/Scheduler (`docs/modules/graph/architecture.md`). 
+- **Cartographer** — _(merged into Graph API)_ Builds identity graphs from SBOM/advisory data. Endpoints now served by `src/Graph/StellaOps.Graph.Api` (`docs/modules/graph/architecture.md`). 
+- **Graph** — Graph API + indexer + Cartographer endpoints, exposing relationship queries and build/overlay operations to UI/CLI/Scheduler (`docs/modules/graph/architecture.md`). 
 - **VulnExplorer** — _(merged into Findings Ledger)_ Explorer for vulnerabilities that combines Concelier data, graph overlays, and Policy results for UI/CLI consumption. Endpoints now served by `src/Findings/StellaOps.Findings.Ledger.WebService`. 
 
 ## Policy & Governance