some comments and fixes

app/database.py

@@ -2,15 +2,17 @@ from sqlmodel import create_engine, SQLModel, Session
 from dotenv import load_dotenv
 import os
 
+# Get database configuration
 load_dotenv()
-
 DATABASE_URL = os.getenv("DATABASE_URL")
 if not DATABASE_URL:
     raise ValueError("DATABASE_URL environment variable is not set")
 
+# Create database engine
 engine = create_engine(DATABASE_URL, echo=True)
 SQLModel.metadata.create_all(engine)
 
+# Get database session
 def get_session():
     with Session(engine) as session:
         yield session