Adds missing return keyword before NextResponse.json()

[soumojit-D48]

Description

Adds missing return keyword before NextResponse.json() in the GET handler of /api/generate/[id]. Without it, when the authenticated user's database record is not found, execution falls through to the catch block and returns a 500 Internal Server Error instead of the intended 404 Not Found.
Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
  Related Issues
  Fixes Unreachable 404 check in DELETE /api/generate/id due to Prisma throwing on missing record #228

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• My changes generate no new warnings
• I have tested my changes locally

### Requested Labels

GSSoC 2026 , gssoc:approved , level:beginner , quality:clean , type:refactor

[netlify]

👷 Deploy request for arcmind-ai pending review.

Visit the deploys page to approve it

Name	Link
🔨 Latest commit	01a21e5

[soumojit-D48]

@SATYAM-PRATIBHAN, Hi Kindly this PR and let me know , Thank You!!