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>

docker-compose.teamhub.yml

@@ -0,0 +1,53 @@
+# Federation overlay: run LegacyHUB behind the TeamHUB gateway on the shared
+# `teamhub_net`. Compared with the standalone dev compose this overlay:
+#   - moves every backing service onto an internal-only network (no host ports);
+#   - reaches the api ONLY via `teamhub_net` (the gateway upstream), never
+#     directly from the host - so spoofing `X-TeamHub-*` is blocked by the network;
+#   - turns on trusted-header identity enforcement (AUTH_REQUIRE_IDENTITY).
+#
+# The shared network must exist first (created by TeamHUB-Platform infra):
+#   docker network create teamhub_net
+#
+# Usage (compose with prod hardening + this federation overlay):
+#   docker compose -f docker-compose.yml -f docker-compose.prod.yml \
+#     -f docker-compose.teamhub.yml --env-file .env.prod up -d --build
+#
+# See RUNBOOK.md "Network model & firewall" for the matching firewall rules.
+
+networks:
+  teamhub_net:
+    external: true
+    name: teamhub_net
+  legacyhub_db:
+    internal: true
+
+services:
+  postgres:
+    ports: !reset []
+    networks: [legacyhub_db]
+
+  minio:
+    ports: !reset []
+    networks: [legacyhub_db]
+
+  opensearch:
+    ports: !reset []
+    networks: [legacyhub_db]
+
+  qdrant:
+    ports: !reset []
+    networks: [legacyhub_db]
+
+  redis:
+    ports: !reset []
+    networks: [legacyhub_db]
+
+  api:
+    # Not published to the host: the gateway reaches the api over teamhub_net.
+    ports: !reset []
+    networks: [legacyhub_db, teamhub_net]
+    environment:
+      AUTH_REQUIRE_IDENTITY: "true"
+
+  worker:
+    networks: [legacyhub_db, teamhub_net]