Harden Celery schedule parsing and startup safety

tests/test_ingestion_tasks.py

@@ -31,6 +31,18 @@ def test_build_periodic_schedule_disabled(settings):
     assert build_periodic_schedule() == {}
 
 
+@pytest.mark.django_db
+def test_build_periodic_schedule_invalid_cron_disables_task_and_logs(settings, caplog):
+    settings.INGESTION_SCHEDULE_ENABLED = True
+    settings.INGESTION_SCHEDULE_CRON = "invalid-cron"
+
+    with caplog.at_level("ERROR"):
+        schedule = build_periodic_schedule()
+
+    assert schedule == {}
+    assert any("Invalid periodic ingestion schedule config. Task disabled." in message for message in caplog.messages)
+
+
 @pytest.mark.django_db
 def test_trigger_incremental_sync_skips_overlapping_runs(settings):
     settings.INGESTION_PREVENT_OVERLAP = True