uncomment env.example value so create works

Author: robdimarco-atxp

backend/env.example

@@ -7,4 +7,4 @@ FRONTEND_PORT=3000
 # Optional: ATXP connection string for image generation and storage
 # If not provided, connection string must be sent via x-atxp-connection-string header
 # The application will return a 400 error if neither env var nor header is provided
-#ATXP_CONNECTION_STRING=your_connection_string_here
+ATXP_CONNECTION_STRING=your_connection_string_here