_is_not_found_error in jail_service did not match the concatenated form
'unknownjailexception' that fail2ban produces when it serialises
UnknownJailException, so JailOperationError was raised instead of
JailNotFoundError and every ban attempt in the import loop failed
individually, skipping all 27 840 IPs before returning an error.
Two changes:
- Add 'unknownjail' to the phrase list in _is_not_found_error so that
UnknownJailException is correctly mapped to JailNotFoundError.
- In blocklist_service.import_source, catch JailNotFoundError explicitly
and break out of the loop immediately with a warning log instead of
retrying on every IP.
