Round 3 fixes: cancelled polling, aggregator invalid_count, filter state, scheduler atomicity, HTTP exception handler, tests

tests/integration/test_health_api.py

@@ -45,3 +45,13 @@ class TestHealthAPI:
         assert isinstance(data["database"], str)
         assert isinstance(data["scheduler"], str)
         assert isinstance(data["version"], str)
+
+    @pytest.mark.asyncio
+    async def test_404_not_found_unified_format(self, client):
+        """测试 404 返回统一格式"""
+        response = await client.get("/api/not-exist")
+        assert response.status_code == 404
+        data = response.json()
+        assert data["code"] == 404
+        assert "message" in data
+        assert data["data"] is None