Update app.py

app.py

@@ -19,7 +19,7 @@ import warnings
 warnings.filterwarnings('ignore')
 
 app = Flask(__name__)
-app.secret_key = 'your-secret-key-here'  # Change this to a secure secret key
+app.secret_key = os.environ.get('FLASK_SECRET_KEY', os.urandom(24).hex())
 
 # Configuration
 UPLOAD_FOLDER = 'static/plots'