Implement PostgreSQL production store path

Add the PostgreSQL backend, migration and stopped-write transfer tools, lease-aware deployment manifests, tenancy declarations, and shared conformance coverage. Persist grouping mutations in durable stores and separate process liveness from database readiness.

tests/test_lifecycle_store_conformance.py

@@ -1,6 +1,6 @@
-"""TEN-WP-0005-T02/T04: one lifecycle contract, both store backends.
+"""TEN-WP-0005-T02/T04: one lifecycle contract, every store backend.
 
-Every test here is parametrised over the in-memory and SQLite stores so the
+Every test here is parametrised over the in-memory, SQLite, and PostgreSQL stores so the
 durable backend cannot silently diverge from the reference semantics -- the
 divergence that matters (CAS, idempotency, retirement guards) is exactly the
 kind a single-backend suite would miss.
@@ -9,6 +9,7 @@ kind a single-backend suite would miss.
 from datetime import UTC, datetime
 
 import pytest
+from postgres_backend import clean_postgres_store
 
 from tenant_engine.domain import (
     CapabilityRole,
@@ -30,11 +31,13 @@ from tenant_engine.store import (
 NOW = datetime(2026, 8, 10, 12, 0, tzinfo=UTC)
 
 
-@pytest.fixture(params=["memory", "sqlite"])
+@pytest.fixture(params=["memory", "sqlite", "postgres"])
 def store(request, tmp_path):
     if request.param == "memory":
         return InMemoryTenantStore()
-    return SQLiteTenantStore(str(tmp_path / "tenant.db"))
+    if request.param == "sqlite":
+        return SQLiteTenantStore(str(tmp_path / "tenant.db"))
+    return clean_postgres_store(tmp_path)
 
 
 @pytest.fixture
@@ -78,6 +81,22 @@ def test_update_persists_and_bumps_version(store, tenant) -> None:
     assert store.get_tenant("t-1").display_name == "Binky Ltd"
 
 
+def test_grouping_mutation_persists(store, tenant) -> None:
+    updated, replayed = store.mutate_tenant(
+        tenant_id="t-1",
+        expected_version=1,
+        mutate=lambda current: current.with_grouping("large", at=NOW),
+        event_type="tenant_grouping_changed",
+        evidence={"actor": "ops", "reason": "growth", "correlation_id": "corr-grouping"},
+        idempotency_key="grouping-large",
+        request_fingerprint="fp-grouping-large",
+    )
+
+    assert replayed is False
+    assert updated.grouping == "large"
+    assert store.get_tenant("t-1").grouping == "large"
+
+
 def test_stale_version_is_rejected(store, tenant) -> None:
     _rename(store, key="k1", version=1)