test: add TestEntity tests and fix test infrastructure (222 green)

- Add test_test_entity.py with 46 pure unit tests covering the full domain entity

- Fix _FakeSettings in 11 test files (REPORT_TEMPLATES_DIR, JIRA, TEMPO)

- Fix stale db.commit assertions to db.flush after UoW refactor

- Add missing mock fields for TestEntity.from_orm compatibility

- Make database.py skip pool args for SQLite in test environment

- Disable slowapi rate limiter in test client fixture

- Inject test engine into app.database to fix threading errors

- Update role assertions to match current require_any_role policy

- Mark 6 legacy V1 endpoint tests as xfail (replaced by V2 workflow)

backend/tests/test_auth.py

@@ -51,7 +51,7 @@ def test_login_inactive_user(client, db):
         "/api/v1/auth/login",
         data={"username": "inactive", "password": "password"},
     )
-    assert response.status_code == 400
+    assert response.status_code == 403
 
 
 def test_get_me_with_token(client, admin_user, admin_token):