修正

backend/app/utils/month_lock.py

@@ -0,0 +1,17 @@
+from datetime import date
+from app.core.database import get_connection
+
+def is_month_locked(target_date: date) -> bool:
+    fiscal_year = target_date.year
+    month = target_date.month
+
+    with get_connection() as conn, conn.cursor() as cur:
+        cur.execute("""
+            SELECT 1
+              FROM month_locks
+             WHERE fiscal_year = %s
+               AND month = %s
+               AND is_locked = true
+        """, (fiscal_year, month))
+
+        return cur.fetchone() is not None