Map trackers by sibling patterns sharing an origin

Tracker patterns detected on the same banner that share initiator
domains are a strong indicator of the same third party. Previously the
mapping worker only checked the global third-party domain catalog, so a
tracker whose domain was not registered there fell through to the
expensive LLM identification step even when a co-located pattern was
already mapped.

Add a matchBySiblingOrigin step that finds other patterns on the same
banner sharing the same initiator domains and reuses their resolved
common third party. It prefers siblings already promoted to an org
third party (the strongest signal) and falls back to siblings carrying
only a catalog link, skipping when the siblings disagree. The step runs
before the catalog domain lookup since an already-qualified sibling is
at least as reliable as a raw domain match.

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

pkg/coredata/detected_tracker.go

@@ -252,6 +252,48 @@ WHERE
 	return nil
 }
 
+func (dts *DetectedTrackers) LoadSiblingPatternIDsByInitiatorDomains(
+	ctx context.Context,
+	conn pg.Querier,
+	cookieBannerID gid.GID,
+	domains []string,
+	excludePatternID gid.GID,
+	limit int,
+) ([]gid.GID, error) {
+	if len(domains) == 0 {
+		return nil, nil
+	}
+
+	q := `
+SELECT DISTINCT tracker_pattern_id
+FROM detected_trackers
+WHERE cookie_banner_id = @cookie_banner_id
+  AND initiator_domain = ANY(@domains)
+  AND tracker_pattern_id IS NOT NULL
+  AND tracker_pattern_id != @exclude_pattern_id
+LIMIT @limit;
+`
+
+	args := pgx.StrictNamedArgs{
+		"cookie_banner_id":   cookieBannerID,
+		"domains":            domains,
+		"exclude_pattern_id": excludePatternID,
+		"limit":              limit,
+	}
+
+	rows, err := conn.Query(ctx, q, args)
+	if err != nil {
+		return nil, fmt.Errorf("cannot load sibling pattern ids: %w", err)
+	}
+
+	ids, err := pgx.CollectRows(rows, pgx.RowTo[gid.GID])
+	if err != nil {
+		return nil, fmt.Errorf("cannot collect sibling pattern ids: %w", err)
+	}
+
+	return ids, nil
+}
+
 func (dts *DetectedTrackers) RelinkByTrackerPatternID(
 	ctx context.Context,
 	tx pg.Tx,