💚(CI) fix build-and-push-backend steps in Docker Hub workflow

Renamed docker/files/usr/local/etc/gunicorn/impress.py to .../meet.py to match the updated
backend source filenames. This resolves the issue where the Dockerfile was attempting
to copy a non-existent file, causing the build to fail.

docker/files/usr/local/etc/gunicorn/meet.py

@@ -1,6 +1,6 @@
 # Gunicorn-django settings
 bind = ["0.0.0.0:8000"]
-name = "impress"
+name = "meet"
 python_path = "/app"
 
 # Run