feat: add settings and async db engine

backend/app/config.py

@@ -0,0 +1,13 @@
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_file=".env", extra="ignore")
+
+    database_url: str
+    ollama_base_url: str
+    session_secret: str
+    port: int = 7777
+
+
+settings = Settings()

backend/app/db.py

@@ -0,0 +1,16 @@
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import DeclarativeBase
+
+from app.config import settings
+
+engine = create_async_engine(settings.database_url, echo=False)
+async_session_maker = async_sessionmaker(engine, expire_on_commit=False)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+async def get_db() -> AsyncSession:
+    async with async_session_maker() as session:
+        yield session