fix: check duplicate photo in AddPhoto

internal/storage/face_gallery_repo.go

@@ -112,6 +112,11 @@ func (r *FaceGalleryRepo) AddPhoto(personID int, photoPath string) error {
 		return err
 	}
 	defer db.Close()
+	// Skip if already exists
+	var existing int
+	if db.QueryRow(`SELECT COUNT(*) FROM face_photos WHERE person_id = ? AND photo_path = ?`, personID, photoPath).Scan(&existing) == nil && existing > 0 {
+		return nil
+	}
 	now := time.Now().Format(time.RFC3339)
 	_, err = db.Exec(`INSERT INTO face_photos(person_id, photo_path, created_at) VALUES(?, ?, ?)`, personID, photoPath, now)
 	return err