feat: align LegacyHUB with TeamHUB platform contract (D2/D4, assets, security)

Close 12 audit-driven platform-compliance gaps on a single branch.

- D4 dispatch: app/integrations/dispatch_client.py participant `legacyhub`,
  emits LegacyhubDocumentIndexed + AssetDerivativeReady after the indexing
  commit (idempotent uuid5), http_inbox route (reindex/tombstone) with
  audit-based dedupe; docs/dispatch-contract.md. Celery+Redis stays intra-module.
- D2 SSO: app/integrations/identity.py validates X-TeamHub-* + role/scope
  mapper; security.py adds trusted-header enforcement (AUTH_REQUIRE_IDENTITY)
  and a scope check on /search; docker-compose.teamhub.yml (external teamhub_net
  + internal db net, api not host-published); RUNBOOK network/firewall section.
- Asset standard: SearchHit/Citation carry asset_id/owner_module; buckets
  renamed teamhub-legacyhub-* (+quarantine/tmp/exports); purge-by-asset_id with
  legal-hold guard (app/indexing/projection.py); OCR-markdown derivative event.
- audit_log model + Alembic 0003 + record_audit on writes (same transaction).
- Secret masking: app/common/json_logger.py recursive mask wired into structlog
  (+ensure_ascii=False); event payloads redacted before persistence.
- Service X-API-Key mandatory on ingest endpoints (defence-in-depth).
- Port: host API 8000->8050 (collision with SalesHUB/MailHUB resolved),
  container still listens on 8000.
- Config: no plaintext secret defaults; fail-loud in non-dev (no value leak).
- Docs drift: README PG 5440, layered-auth note, 5173 removed from CORS;
  ingest/folder gated by ENABLE_FOLDER_INGEST (410 by default).
- ADRs: layers mapping, shared-core extraction, UI locale (RU-first).

Tests: 78 passing (ruff, compileall, pytest, tsc, vite build, compose config).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/ingestion/pipeline.py

@@ -216,6 +216,14 @@ def process_document_id(  # noqa: PLR0911, PLR0912, PLR0915
             )
         )
 
+    # Inter-module event (D4) - after commit, best-effort; never fails the doc.
+    try:
+        from app.integrations.dispatch_client import emit_after_indexing  # noqa: PLC0415
+
+        emit_after_indexing(document_id)
+    except Exception as exc:  # noqa: BLE001
+        logger.warning("pipeline.emit_failed", document_id=str(document_id), error=str(exc))
+
     return {"status": DocumentStatus.INDEXING_COMPLETED, "chunks": len(chunk_records)}