Add a /version Endpoint

Create a simple /version endpoint to quickly check which version of the service is running.

This is a great, self-contained task for a new contributor to get familiar with adding an endpoint to the FastAPI application.

**Acceptance Criteria**
- A new Pydantic model VersionResponse is added to artisan_engine/models.py.
- A new GET endpoint is created at /version in main.py.
- The endpoint returns a JSON response containing the version from the application's configuration.

Example response:
```json
{
"version": "0.1.0"
}
```