fix: resolve schemathesis and live test failures

- Add 403 response to all RBAC-gated endpoints (schemathesis UndefinedStatusCode)
- Add 400 response to all endpoints accepting JSON bodies (malformed input)
- Add required 'title' field to schemathesis.toml for schemathesis 4.15+
- Add xdist_group markers to live tests with module-scoped fixtures to
  prevent xdist from distributing them across workers (fixture isolation)

tests/live/test_health_live.py

@@ -97,6 +97,7 @@ async def token(live_client):
 
 
 @pytest.mark.live
+@pytest.mark.xdist_group("health_live")
 class TestHealthLive:
     """Live integration tests — real DB, real Docker check, real task state."""
 

tests/live/test_service_isolation_live.py

@@ -128,6 +128,7 @@ async def token(live_client):
 
 
 @pytest.mark.live
+@pytest.mark.xdist_group("service_isolation_live")
 class TestCollectorLiveIsolation:
     """Real collector behaviour against the actual Docker daemon."""
 
@@ -203,6 +204,7 @@ class TestCollectorLiveIsolation:
 
 
 @pytest.mark.live
+@pytest.mark.xdist_group("service_isolation_live")
 class TestIngesterLiveIsolation:
     """Real ingester against real DB and real filesystem."""
 
@@ -312,6 +314,7 @@ class TestIngesterLiveIsolation:
 
 
 @pytest.mark.live
+@pytest.mark.xdist_group("service_isolation_live")
 class TestAttackerWorkerLiveIsolation:
     """Real attacker worker against real DB."""
 
@@ -360,6 +363,7 @@ class TestAttackerWorkerLiveIsolation:
 
 
 @pytest.mark.live
+@pytest.mark.xdist_group("service_isolation_live")
 class TestSnifferLiveIsolation:
     """Real sniffer against the actual host network stack."""
 
@@ -396,6 +400,7 @@ class TestSnifferLiveIsolation:
 
 
 @pytest.mark.live
+@pytest.mark.xdist_group("service_isolation_live")
 class TestApiLifespanLiveIsolation:
     """Real API lifespan against real DB and real host state."""
 
@@ -442,6 +447,7 @@ class TestApiLifespanLiveIsolation:
 
 
 @pytest.mark.live
+@pytest.mark.xdist_group("service_isolation_live")
 class TestCascadeLiveIsolation:
     """Verify that real component failures do not cascade."""