Global backend=systemd in jail.local silently breaks file-based jails.
Added required backend=polling to config, diagnostic command, and warning.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
New guide for custom access-log-based fail2ban jail that catches
rapid-fire 404 vulnerability scanners missed by default error-log jails.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
