[Bug]: Issue Title: Implement Gemini API for Chatbot Functionality (chatbot.dart)

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The chatbot feature in the app (chatbot.dart) is currently non-functional due to the lack of an API implementation. Integrate the Gemini API to enable interactive conversations in the chatbot, allowing users to receive responses based on their input.

### Expected behavior

Without a working chatbot, users cannot benefit from automated assistance or interaction. Implementing the Gemini API will significantly improve the app's functionality and user engagement by enabling real-time chatbot interactions.

Integrate the Gemini API for handling chatbot interactions.
Implement the logic to send user input to the Gemini API and process the response.
Ensure the response from the API is displayed in the chat UI in real-time.
Handle API keys securely and implement error handling.

Start by reading chatbot.dart to understand the existing chat UI and entry points for user input and displayed responses. Define completion around sending input to the Gemini API, showing responses in real time, securely handling API keys, and reporting errors; verify the full interaction in the app.

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