refactor: initialize expert catalog from initdb

backend/internal/initdb/new.go

@@ -4,5 +4,10 @@ import "gorm.io/gorm"
 
 // New initializes the default database records.
 func New(database *gorm.DB) error {
-	return InitUser(database)
+	return database.Transaction(func(tx *gorm.DB) error {
+		if err := InitUser(tx); err != nil {
+			return err
+		}
+		return InitExpert(tx)
+	})
 }