Add repo-root pytest config so async tests run from root

pytest.ini

@@ -0,0 +1,10 @@
+[pytest]
+# Ensure pytest-asyncio is in auto mode for async tests without explicit markers.
+asyncio_mode = auto
+
+# Run the backend test suite from the repository root.
+testpaths = backend/tests
+pythonpath = backend
+
+# Keep coverage output consistent with backend/pyproject.toml settings.
+addopts = --cov=backend/app --cov-report=term-missing