feat: introduced plans pricing

db/models/addons.py

@@ -0,0 +1,13 @@
+from sqlalchemy import FLOAT, INTEGER, TEXT
+from sqlalchemy.orm import Mapped, mapped_column
+
+from db.base import Base
+
+
+class Addon(Base):
+    __tablename__ = "addons"
+
+    id: Mapped[str] = mapped_column(TEXT, nullable=False, unique=True, primary_key=True)
+    name: Mapped[str] = mapped_column(TEXT, nullable=False, unique=False)
+    price: Mapped[float] = mapped_column(FLOAT, nullable=False)
+    free_threshold: Mapped[int] = mapped_column(INTEGER, default=-1)