feat(bot): add async DB and FSM state handling

bot/db/__init__.py

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+

bot/db/base.py

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+from sqlalchemy.orm import DeclarativeBase
+
+
+class Base(DeclarativeBase):
+    pass

bot/db/init.py

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+from bot.db import models  # noqa: F401
+from bot.db.base import Base
+from bot.db.session import engine
+
+
+async def init_db() -> None:
+    async with engine.begin() as connection:
+        await connection.run_sync(Base.metadata.create_all)

bot/db/models.py

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+from datetime import datetime, timezone
+
+from sqlalchemy import BigInteger, Boolean, DateTime, String
+from sqlalchemy.orm import Mapped, mapped_column
+
+from bot.db.base import Base
+
+
+def utc_now() -> datetime:
+    return datetime.now(timezone.utc)
+
+
+class User(Base):
+    __tablename__ = "users"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    telegram_id: Mapped[int] = mapped_column(BigInteger, unique=True, index=True)
+    username: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    first_name: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    last_name: Mapped[str | None] = mapped_column(String(255), nullable=True)
+    is_admin: Mapped[bool] = mapped_column(Boolean, default=False)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=utc_now)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=utc_now,
+        onupdate=utc_now,
+    )

bot/db/session.py

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+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+
+from bot.config import DATABASE_URL
+
+engine = create_async_engine(DATABASE_URL)
+async_session = async_sessionmaker(engine, expire_on_commit=False, class_=AsyncSession)