Mount config.yml into Docker container and provide example template.
Changes:
- Mount config.yml as read-only volume in docker-compose.yml
- Create config.example.yml template for users
- Add config.yml to .gitignore (contains sensitive settings)
- Update README.md with config file setup instructions
Fixes 'Config file not found' error in Docker deployment.
Users should:
1. Copy config.example.yml to config.yml
2. Edit config.yml with their settings
3. Run docker compose up -d