Replace deprecated datetime.datetime.utcnow() with timezone-aware UTC timestamps

[Kaap10]

Description

In Python 3.12+, datetime.datetime.utcnow() has been deprecated and triggers runtime DeprecationWarning notices during test execution.

Proposed Solution

Replace all occurrences of datetime.datetime.utcnow() in backend/app/storage/repository.py and backend/app/benchmarks/runner.py with timezone-aware UTC timestamps:

from datetime import datetime, timezone

# Use timezone-aware UTC timestamp:
datetime.now(timezone.utc)

Relevant Files

• backend/app/storage/repository.py
• backend/app/benchmarks/runner.py

Acceptance Criteria

• Replace datetime.datetime.utcnow() across all backend modules.
• Run python -m pytest and verify that all 13 tests pass with 0 deprecation warnings.