Update app.py

app.py

@@ -1,6 +1,6 @@
 import subprocess
-
-def start_mlflow_server(host="0.0.0.0", port=7860, backend_uri="sqlite:////app/mlflow_data/mlflow.db", artifact_root="/app/mlflow_data/mlruns"):
+import os
+def start_mlflow_server(host="0.0.0.0", port=7860, backend_uri=os.getenv("backend_uri"), artifact_root="/app/mlflow_data/mlruns"):
     """
     Starts an MLflow tracking server with authentication using --app-name basic-auth.