Upload CSV to replace message_logs

This will truncate the table and import your CSV. Date columns like CreatedOn/SentOn will be converted to YYYY-MM-DD HH:MM:SS (e.g., 8/5/2025 16:00:00 → 2025-08-05 16:00:00).

CSV header names must match columns in message_logs. Extra columns are ignored; missing columns are not inserted.