feat(api): add warnings field to response models

Add optional warnings field to:
- SimulateTriggerResponse
- JobStatusResponse

Co-Authored-By: Claude <noreply@anthropic.com>

tests/unit/test_response_models.py

@@ -0,0 +1,32 @@
+from api.main import SimulateTriggerResponse, JobStatusResponse, JobProgress
+
+def test_simulate_trigger_response_accepts_warnings():
+    """Test SimulateTriggerResponse accepts warnings field."""
+    response = SimulateTriggerResponse(
+        job_id="test-123",
+        status="completed",
+        total_model_days=10,
+        message="Job completed",
+        deployment_mode="DEV",
+        is_dev_mode=True,
+        warnings=["Rate limited", "Skipped 2 dates"]
+    )
+
+    assert response.warnings == ["Rate limited", "Skipped 2 dates"]
+
+def test_job_status_response_accepts_warnings():
+    """Test JobStatusResponse accepts warnings field."""
+    response = JobStatusResponse(
+        job_id="test-123",
+        status="completed",
+        progress=JobProgress(total_model_days=10, completed=10, failed=0, pending=0),
+        date_range=["2025-10-01"],
+        models=["gpt-5"],
+        created_at="2025-11-01T00:00:00Z",
+        details=[],
+        deployment_mode="DEV",
+        is_dev_mode=True,
+        warnings=["Rate limited"]
+    )
+
+    assert response.warnings == ["Rate limited"]