Additional Offerings Section

## Description:
Shows options for online appointments or vaccination bookings.
![Content](https://github.com/user-attachments/assets/d11e6a1e-5ebb-4100-9162-0c6533322dd2)

## Components:

- Button for "Online-Termin für Impfungen" (`ElevatedButton`).

## Development Notes:

- Use Flutter's `ElevatedButton` with custom styling.
- Implement navigation or API calls on button click.