Maintain backward compatibility with WEBUI_JWT_SECRET_KEY for the time being

backend/start.sh

@@ -6,7 +6,7 @@ cd "$SCRIPT_DIR" || exit
 KEY_FILE=.webui_secret_key
 
 PORT="${PORT:-8080}"
-if ["$WEBUI_SECRET_KEY" = ""]; then
+if ["$WEBUI_SECRET_KEY $WEBUI_JWT_SECRET_KEY" = " "]; then
   echo No WEBUI_SECRET_KEY provided
 
   if ! [ -e "$KEY_FILE" ]; then