test: add regression test for RAG query endpoint ensuring time import is present

[Pcmhacker-piro]

Summary
Closes #736
The import time was added in a prior commit to fix a NameError from time.monotonic() in the RAG query endpoint. This PR adds a dedicated regression test suite (backend/tests/test_rag_query.py) that would catch this class of import errors in the future.
Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor
• Tests
• Infra / CI
  Checklist
• I have read CONTRIBUTING.md
• My code follows the project style
• I have added/updated tests where relevant
• Tests/lint pass locally (if available)
• I have not committed .env or any secrets
• I have updated documentation if needed
  Screenshots (if UI change)
  N/A
  CHANGED FILES
• backend/tests/test_rag_query.py (new file, 129 lines)
  COMMITS
• e4f9821 - test: add regression test for RAG query endpoint ensuring time import is present
  TESTING PERFORMED
  cd /tmp/aegisai/backend && python3 -m pytest tests/test_rag_query.py -v --no-header

Result: 4 passed in 0.20s

FINAL STATUS

• Branch Name: fix/rag-query-time-import-test (also pushed to fix/rag-query-regression-test)
• Commit Hash: e4f9821
• PR Created: No (token lacks createPullRequest scope)
• Ready for Review: Yes

[Pcmhacker-piro]

@SdSarthak

the checks have passed. Could you please review and approve the pending workflows when you have a chance? Thank you!