Move history archive max timestamp query into repository

backend/app/repositories/history_archive_repo.py

@@ -36,6 +36,15 @@ async def archive_ban_event(
     return inserted
 
 
+async def get_max_timeofban(db: aiosqlite.Connection) -> int | None:
+    """Return the latest archived ban timestamp or ``None`` when empty."""
+    async with db.execute("SELECT MAX(timeofban) FROM history_archive") as cursor:
+        row = await cursor.fetchone()
+    if row is None or row[0] is None:
+        return None
+    return int(row[0])
+
+
 async def get_archived_history(
     db: aiosqlite.Connection,
     since: int | None = None,