- Introduced make commands for E2E tests using Testcontainers and Schemathesis.
- Updated `.env.demo` with configurable OAuth settings for Google and GitHub.
- Enhanced `README.md` with updated environment setup instructions.
- Added E2E testing dependencies and markers in `pyproject.toml` for real PostgreSQL and API contract validation.
- Included new libraries (`arrow`, `attrs`, `docker`, etc.) for testing and schema validation workflows.