The blocklist import service targets a dedicated jail called
'blocklist-import' (BLOCKLIST_JAIL constant in blocklist_service.py),
but that jail was never defined in the dev fail2ban configuration.
Every import attempt immediately failed with UnknownJailException.
Add Docker/fail2ban-dev-config/fail2ban/jail.d/blocklist-import.conf:
a manual-ban jail with no log-based detection that accepts banip
commands only, using iptables-allports with a 1-week bantime.
Also track the new file in .gitignore (whitelist) and fix a
pre-existing blank-line-with-whitespace lint error in setup_service.py.