hoàn thành bước tạo docker compose

backend/app/main.py

@@ -3,14 +3,13 @@ from contextlib import asynccontextmanager
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
-from .database import Base, engine
 from .routers import annotations, auth, pdfs
 
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
-    # Create all tables on startup (use Alembic for migrations in production)
-    Base.metadata.create_all(bind=engine)
+    # Tables are managed by Alembic migrations.
+    # Run: alembic upgrade head  (done by docker-compose entrypoint)
     yield