fix : replaced deprecated datetime.utcnow with timezone-aware alternative in code_review

[tmdeveloper007]

Summary of What Has Been Done

Replaced all uses of the deprecated datetime.utcnow() with the timezone-aware datetime.now(timezone.utc) in src/utils/code_review.py.

Changes Made

• Changed from datetime import datetime to from datetime import datetime, timezone in src/utils/code_review.py
• Replaced 5 occurrences of datetime.utcnow() with datetime.now(timezone.utc):
  • Line 103: submitted_at timestamp
  • Line 131: review_id generation
  • Line 137: started_at timestamp
  • Line 181: created_at timestamp
  • Line 252: completed_at timestamp

Impact it Made

Eliminates deprecation warnings in Python 3.12+ and ensures correct timezone-aware timestamps in the code review system.

Closes #1494

Note: Please assign this PR to the tmdeveloper007 account.

[vercel]

Someone is attempting to deploy a commit to the komalsony234-1530's projects Team on Vercel.

A member of the Team first needs to authorize it.