Evaluation: Extend export functionality

[AkhileshNegi]

Is your feature request related to a problem?

Related to Frontend Issue. We need a new CSV export format that groups repeated questions horizontally, but the current API only supports row-based export, where each iteration appears as a separate row.

Describe the solution you'd like
Extend the existing export API to support a grouped format with columns:
Golden Question, Ground Truth, Answer 1, Answer 2, Answer 3, Answer 4, Answer 5.

This requires:

• A new query parameter (e.g., format=grouped) or a separate endpoint
• Leveraging question_id mentioned in Evaluation: Parent ID to run traces #544 to collate repeated questions

Screenshot

[vprashrex]

Okay i will check this.