fix: ruff findings

src/fenris/projection.py

@@ -24,9 +24,9 @@ Criteria: PR-1–PR-17, CI-4.
 """
 import sqlite3
 from dataclasses import dataclass, field
-from datetime import datetime, timedelta, timezone
+from datetime import datetime, timedelta
 from enum import Enum
-from typing import Any, Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional
 
 from .monitoring_periods import interval_within_one_monitoring_period