Match sibling trackers on first-party origin

Sibling matching is an org-local co-occurrence signal: two patterns
served from the same origin on one banner are likely the same vendor,
even when that origin is the site's own (first-party) host. First-party
filtering only protects the global catalog (domain) match, where a
proxied tracker would otherwise hit the site owner's own entry. It now
runs solely before matchByDomain, so matchBySiblingOrigin sees the
unfiltered domains and promotion happens for patterns detected on the
banner's own origin.

Resolve the sibling's direct org third party and its catalog third party
as independent signals, so a single shared org third party no longer
short-circuits the common-pattern backfill.

Make the shared test fixtures unique per tenant: common_third_parties
and common_tracker_patterns are global with unique indexes, so parallel
tests previously collided on name, slug, and pattern. Also align the
sibling tests' stored initiator domains with production, which records
the eTLD+1.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/coredata/third_party.go

@@ -1418,7 +1418,6 @@ WHERE
 	%s
 	AND organization_id = @organization_id
 	AND common_third_party_id = @common_third_party_id
-	AND snapshot_id IS NULL
 ORDER BY id ASC
 LIMIT 1;
 `