Integrates the checker-blacklist module behind a new POST /blacklist/domain
endpoint that aggregates reputation/blocklist sources for a given domain,
plus a SvelteKit UI under /blacklist/domain mirroring the existing IP
blacklist flow. Per-source credentials (VirusTotal, Safe Browsing) are
exposed as CLI flags; free sources run unconditionally.
Closes: #96
Implements parsing, scoring, CLI output, and UI display for the DMARC
np= tag (DMARCbis draft-ietf-dmarc-dmarcbis), which controls policy for
NXDOMAIN subdomains independently of sp=. The score deducts 15 points
from the base and awards them back when np= is absent (good default) or
its strength is equal to or stricter than the effective sp=/p= policy.
