Add integration test for creator detail returning 404 with correct error shape

[chiscookeke11]

Summary

• Added a new GET /api/v1/creators/:id endpoint to return public creator profile details.
• Added creatorProfileExists() to verify creator existence by ID or handle before fetching profile details.
• Standardized missing creator responses to return a 404 NOT_FOUND error envelope with the documented response shape.
• Registered the route with parameter validation, metrics, cache-control, and a 405 Method Not Allowed handler.
• Added an integration test covering the 404 response and standardized error payload for non-existent creators.

Testing

• pnpm lint
• pnpm build
• pnpm exec prisma generate when schema or generated types changed

Checklist

• Linked issue or backlog item
• No secrets or live credentials added
• Docs updated if setup or env changed
• Change is scoped to one problem

Closes #553

[drips-wave]

@chiscookeke11 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits