added db connection error handling.

backend/app/database.py

@@ -7,9 +7,14 @@ from sqlalchemy.sql import func
 import os
 from sqlalchemy.exc import IntegrityError
 from werkzeug.security import check_password_hash, generate_password_hash
+from backend.config import Config  # Add this import
 
 # SQLAlchemy setup
-DATABASE_URL = os.environ.get('DATABASE_URL')
+DATABASE_URL = os.environ.get('DATABASE_URL') or Config.SQLALCHEMY_DATABASE_URI
+
+if not DATABASE_URL or DATABASE_URL.strip() == "":
+    raise ValueError("DATABASE_URL is not set or is empty. Please set it as an environment variable or secret.")
+
 engine = create_engine(DATABASE_URL)
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 Base = declarative_base()