Feature: Add support for the Gemini model in a way that also allows free-tier users to access and use it.

**Feature:** Add support for the **Gemini model** so that users with a free Gemini API key can also use the project.  

- Implementation must respect the free-tier limits (e.g., no more than 15 requests per minute).  
- Ensure proper constraints and rate-limiting to avoid violating free usage policies.
