feat: add pytest-asyncio, freezegun, schemathesis, pytest-cov to test toolchain

tests/api/test_schemathesis.py

@@ -0,0 +1,22 @@
+"""
+Schemathesis contract tests.
+
+Generates requests from the OpenAPI spec and verifies that no input causes a 5xx.
+
+Currently scoped to `not_a_server_error` only — full response-schema conformance
+(including undocumented 401 responses) is blocked by DEBT-020 (missing error
+response declarations across all protected endpoints). Once DEBT-020 is resolved,
+replace the checks list with the default (remove the argument) for full compliance.
+
+Requires DECNET_DEVELOPER=true (set in tests/conftest.py) to expose /openapi.json.
+"""
+import schemathesis
+from schemathesis.checks import not_a_server_error
+from decnet.web.api import app
+
+schema = schemathesis.openapi.from_asgi("/openapi.json", app)
+
+
+@schemathesis.pytest.parametrize(api=schema)
+def test_schema_compliance(case):
+    case.call_and_validate(checks=[not_a_server_error])