fix: return created routine data in response

[mrdeyroy]

📌 Description

This PR fixes a bug in routineController.js where the createRoutine API was incorrectly passing the newly created routine as a second argument to res.json(), causing Express to ignore it. The response shape has been updated to correctly return the data inside a single object.

🔗 Related Issue

Closes ##441

🛠 Changes Made

• Updated the response shape in backend/controllers/routineController.js for the createRoutine endpoint.
• Ensured the data payload returns the newRoutine object.
• Adhered strictly to the consistent JSON response format without modifying any other files or variables.

📸 Screenshots (if applicable)

N/A - Backend API response fix only.

✅ Checklist

• Code runs locally
• Followed project structure
• No console errors
• Properly tested changes
• Linked the issue

🚀 Notes for Reviewers

N/A