feat: added zod-validation

[abhijit1859]

Description

Added server-side request validation middleware using Zod.
Validates incoming requests for user, message, and chatbot endpoints to ensure required fields (name, email, message, userId) are present and properly formatted.
Returns 400 Bad Request with detailed error messages for invalid request

Semver Changes

• Patch (bug fix, no new features)
• Minor (new features, no breaking changes)
• Major (breaking changes)

#14

List any issues that this pull request closes.

Checklist

• I have read the Contributing Guidelines.

[MD-IRFAN-RAJ]

@abhijit1859 resolve conflicts

[abhijit1859]

done

[MD-IRFAN-RAJ]

@all-contributors please add @abhijit1859 @nitingupta95 for code

[allcontributors]

@MD-IRFAN-RAJ

I've put up a pull request to add @abhijit1859! 🎉