Initial MVP: full-stack music discovery app

Backend (FastAPI):
- User auth with email/password and Spotify OAuth
- Spotify playlist import with audio feature extraction
- AI recommendation engine using Claude API with taste profiling
- Save/bookmark recommendations
- Rate limiting for free tier (10 recs/day, 1 playlist)
- PostgreSQL models with Alembic migrations
- Redis-ready configuration

Frontend (React 19 + TypeScript + Vite + Tailwind):
- Landing page, auth flows (email + Spotify OAuth)
- Dashboard with stats and quick discover
- Playlist management and import from Spotify
- Discover page with custom query support
- Recommendation cards with explanations and save toggle
- Taste profile visualization
- Responsive layout with mobile navigation
- PWA-ready configuration

Infrastructure:
- Docker Compose with PostgreSQL, Redis, backend, frontend
- Environment-based configuration

backend/app/core/database.py

@@ -0,0 +1,21 @@
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
+from sqlalchemy.orm import DeclarativeBase
+
+from app.core.config import settings
+
+engine = create_async_engine(settings.DATABASE_URL, echo=settings.DEBUG)
+async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+async def get_db() -> AsyncSession:
+    async with async_session() as session:
+        try:
+            yield session
+            await session.commit()
+        except Exception:
+            await session.rollback()
+            raise