Alembic sous python/fastapi

Voici mes fichiers :
app/core/db.py
```python
# from collections.abc import AsyncGenerator
import contextlib
from collections.abc import AsyncGenerator, AsyncIterator
from typing import Annotated, Any

from fastapi import Depends
from sqlalchemy import MetaData
from sqlalchemy.ext.asyncio import (
    AsyncConnection,
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)
from sqlalchemy.orm import DeclarativeBase

from app.core.config import settings
from app.utils.logger import logger


class Base(DeclarativeBase):
    # https://docs.sqlalchemy.org/en/14/orm/extensions/asyncio.html#preventing-implicit-io-when-using-asyncsession
    __mapper_args__ = {"eager_defaults": True}
```

app/models/visitor.py
```python
import re

from sqlalchemy import Boolean, Column, DateTime, Integer, String, func
from sqlalchemy.dialects.postgresql import UUID

from app.core.db import Base
from app.utils.hash import hash_get_from, hash_verify


class Visitor(Base):
    __tablename__ = "visitor"
    id = Column(Integer, primary_key=True)
    uid = Column(
        UUID, unique=True, index=True, nullable=False, server_default=func.gen_random_uuid()
    )
    email = Column(String(100), unique=True, index=True, nullable=False)
    username_managed = Column(String(50), nullable=False)
    hashed_password = Column(String(100), nullable=False)
    # hashed_password = Column(String(100), nullable=False)
    is_active = Column(Boolean, nullable=False, default=False)
    is_superuser = Column(Boolean, nullable=False, default=False)
    created_at = Column(DateTime(timezone=True), server_default=func.now())
    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
```

alembic/env.py
```python
import asyncio
from logging.config import fileConfig

from sqlalchemy import pool
from sqlalchemy.engine import Connection
from sqlalchemy.ext.asyncio import async_engine_from_config

from alembic import context
from app.core.config import settings
from app.core.db import Base
from app.models import *

# this is the Alembic Config object, which provides
# access to the values within the .ini file in use.
config = context.config

config.set_main_option("sqlalchemy.url",settings.DB_URL)

# Interpret the config file for Python logging.
# This line sets up loggers basically.
if config.config_file_name is not None:
    fileConfig(config.config_file_name)

# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
# target_metadata = mymodel.Base.metadata
target_metadata = Base.metadata

# other values from the config, defined by the needs of env.py,
# can be acquired:
# my_important_option = config.get_main_option("my_important_option")
# ... etc.


def run_migrations_offline() -> None:
    """Run migrations in 'offline' mode.

    This configures the context with just a URL
    and not an Engine, though an Engine is acceptable
    here as well.  By skipping the Engine creation
    we don't even need a DBAPI to be available.

    Calls to context.execute() here emit the given string to the
    script output.

    """
    url = config.get_main_option("sqlalchemy.url")
    context.configure(
        url=url,
        target_metadata=target_metadata,
        literal_binds=True,
        dialect_opts={"paramstyle": "named"},
    )

    with context.begin_transaction():
        context.run_migrations()


def do_run_migrations(connection: Connection) -> None:
    context.configure(connection=connection, target_metadata=target_metadata)

    with context.begin_transaction():
        context.run_migrations()


async def run_async_migrations() -> None:
    """In this scenario we need to create an Engine
    and associate a connection with the context.

    """

    connectable = async_engine_from_config(
        config.get_section(config.config_ini_section, {}),
        prefix="sqlalchemy.",
        poolclass=pool.NullPool,
    )

    async with connectable.connect() as connection:
        await connection.run_sync(do_run_migrations)

    await connectable.dispose()


def run_migrations_online() -> None:
    """Run migrations in 'online' mode."""

    asyncio.run(run_async_migrations())


if context.is_offline_mode():
    run_migrations_offline()
else:
    run_migrations_online()
```

Ou est mon erreur ?