Add ntfy (https://ntfy.sh) push notifications alongside email. Each backup profile can configure its own ntfy topic, server, and access token independently. - New profile fields: ntfy_topic, ntfy_server (default ntfy.sh), ntfy_token (optional, for private topics) - NotificationSender sends both email and ntfy in parallel - Uses priority 5 (urgent) for failures, 3 (default) for success - Includes backup status emoji, profile name, type, archive, size - 10-second timeout to prevent blocking backup completion - SQL migration 01.18.00 adds columns to profiles table