Some more refactoring

src/models/category.py

@@ -1,6 +1,6 @@
 from pydantic import Field, computed_field
 from sqlalchemy import ForeignKey, String, UniqueConstraint
-from sqlalchemy.orm import Mapped, Session, mapped_column, relationship
+from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from src.models.common import BaseModelDb, ExportBaseModel, hashify
 
@@ -54,8 +54,3 @@ class CategoryDb(BaseModelDb):
     )
     children = relationship("CategoryDb", back_populates="parent")
     budgets = relationship("CategoryBudgetDb", back_populates="category")
-
-
-def add_category(session: Session, category_name: str):
-    category = Category.from_str(category_name)
-    session.add(category)