feat(chatbot): chatbot prompt enhancenent

[AritraDey-Dev]

Fixes Issue #55

Changes proposed

• Added personality and clear boundaries to MindGuide bot
• Implemented strict mental health focus with character-based responses
• Added fallback response for off-topic questions
• Improved prompt security against injection attempts

Check List (Check all the applicable boxes)

• My code follows the code style of this project.
• My change requires changes to the documentation.
• I have updated the documentation accordingly.
• All new and existing tests passed.
• This PR does not contain plagiarized content.
• The title of my pull request is a short description of the requested changes.

[sristy17]

Great job, @AritraDey-Dev! 🎉 Thank you for submitting your pull request. Your contribution is valuable and we appreciate your efforts to improve our project.

We will promptly review your changes and offer feedback. Keep up the excellent work! Kindly remember to check our contributing guidelines

[AritraDey-Dev]

follow up PR of #93