refactor(tests): reorganize tests into unittest/ and e2e/ directories

- Move all unit tests from tests/ to tests/unittest/
- Add tests/e2e/ directory for end-to-end tests
- Update conftest.py for new test structure
- Add new tests for auth dependencies, policies, route injection
- Add new tests for run callbacks, create store, execution artifacts
- Remove obsolete tests for deleted persistence layer

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/tests/unittest/test_security_scanner.py

@@ -0,0 +1,17 @@
+from types import SimpleNamespace
+
+import pytest
+
+from deerflow.skills.security_scanner import scan_skill_content
+
+
+@pytest.mark.anyio
+async def test_scan_skill_content_blocks_when_model_unavailable(monkeypatch):
+    config = SimpleNamespace(skill_evolution=SimpleNamespace(moderation_model_name=None))
+    monkeypatch.setattr("deerflow.skills.security_scanner.get_app_config", lambda: config)
+    monkeypatch.setattr("deerflow.skills.security_scanner.create_chat_model", lambda **kwargs: (_ for _ in ()).throw(RuntimeError("boom")))
+
+    result = await scan_skill_content("---\nname: demo-skill\ndescription: demo\n---\n", executable=False)
+
+    assert result.decision == "block"
+    assert "manual review required" in result.reason