chore(docker): set default user to non-root in Dockerfile

Updated the Dockerfile to set the default user to a non-root user for improved security practices. This change ensures that the application runs with limited privileges, reducing potential risks.

Additionally, renamed `app.py` to `main.py` to better reflect its role as the main entry point of the FastAPI application.

Dockerfile

@@ -24,6 +24,7 @@ COPY --chown=user . /app
 
 # Document the port that the application will listen on
 EXPOSE 9099
+USER user
 
 # Define the command to run the FastAPI application using uvicorn
 CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "9099"]