ImportError: ImportError: cannot import name 'BaseSettings' from 'pydantic'

Root cause

The project is running Pydantic v2, where BaseSettings was removed from the pydantic package and migrated into the separate pydantic-settings distribution. app/core/config.py still uses the Pydantic v1 import path: `from pydantic import BaseSettings, Field`.

Minimal fix

Add `pydantic-settings` to the project dependencies, install it in the environment, and update the settings module to import `BaseSettings` from `pydantic_settings` while keeping other pydantic imports unchanged, e.g. `from pydantic import Field` and `from pydantic_settings import BaseSettings`. Then rerun `pytest tests/test_config.py -q`.