Remove unused asyncio import from log_service

Clean log_service.py by deleting the unused asyncio import and mark Task 24 completed in Docs/Tasks.md.

backend/app/services/log_service.py

@@ -6,7 +6,6 @@ fail2ban socket operations.
 
 from __future__ import annotations
 
-import asyncio
 from app.utils.async_utils import run_blocking
 import re
 from pathlib import Path