Add tracker mapping worker and initiator domain extraction

Poll-based worker that maps org-scoped tracker patterns to the
common knowledge base via pattern matching and domain-based
attribution. Populates initiator_domain on detected trackers
at report time. Resolves org-scoped vendors through the common
third party link.

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

pkg/coredata/detected_tracker.go

@@ -16,6 +16,7 @@ package coredata
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"maps"
 	"time"
@@ -151,6 +152,33 @@ WHERE
 	return count, nil
 }
 
+func (dts *DetectedTrackers) LoadCommonThirdPartyIDByTrackerPatternID(
+	ctx context.Context,
+	conn pg.Querier,
+	trackerPatternID gid.GID,
+) (*gid.GID, error) {
+	q := `
+SELECT DISTINCT ctpd.common_third_party_id
+FROM detected_trackers dt
+JOIN common_third_party_domains ctpd ON ctpd.domain = dt.initiator_domain
+WHERE dt.tracker_pattern_id = @tracker_pattern_id
+  AND dt.initiator_domain IS NOT NULL
+LIMIT 1;
+`
+
+	args := pgx.StrictNamedArgs{"tracker_pattern_id": trackerPatternID}
+
+	var commonThirdPartyID gid.GID
+	if err := conn.QueryRow(ctx, q, args).Scan(&commonThirdPartyID); err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("cannot load common third party ID by tracker pattern: %w", err)
+	}
+
+	return &commonThirdPartyID, nil
+}
+
 func (dts *DetectedTrackers) RelinkByTrackerPatternID(
 	ctx context.Context,
 	tx pg.Tx,