fix(deploy): wire the Robokassa direct rail into the prod deploy + rollback

The Robokassa credentials reached only the test contour (ci.yaml → TEST_
secrets). The prod-deploy / prod-rollback workflows and write-prod-env.sh
never rendered BACKEND_ROBOKASSA_*, so on prod the shop login was empty and
the direct RUB rail stayed disabled — the PROD_BACKEND_ROBOKASSA_* secrets
went nowhere.

Export the shop login + Password1/Password2 (secrets) and a
BACKEND_ROBOKASSA_TEST flag (a variable, so go-live is a flag flip not a
secret rotation) from both prod workflows, and emit the four ROBOKASSA_*
vars from write-prod-env.sh (the shared deploy/rollback env renderer) so a
rollback keeps the rail up. The compose already maps ROBOKASSA_* →
BACKEND_ROBOKASSA_*. Document the new secrets/variable in the deploy README
and .env.example. Password3 (Robokassa's JWT-invoice API) is unused.

deploy/write-prod-env.sh

@@ -52,6 +52,10 @@ export APP_VERSION='$APP_VERSION'
 export TELEGRAM_BOT_TOKEN='$TELEGRAM_BOT_TOKEN'
 export TELEGRAM_MINIAPP_URL='$TELEGRAM_MINIAPP_URL'
 export GATEWAY_VK_APP_SECRET='$GATEWAY_VK_APP_SECRET'
+export ROBOKASSA_MERCHANT_LOGIN='$ROBOKASSA_MERCHANT_LOGIN'
+export ROBOKASSA_PASSWORD1='$ROBOKASSA_PASSWORD1'
+export ROBOKASSA_PASSWORD2='$ROBOKASSA_PASSWORD2'
+export ROBOKASSA_TEST='$ROBOKASSA_TEST'
 export VITE_VK_APP_ID='$VITE_VK_APP_ID'
 export VITE_VK_ID_REDIRECT_URL='$VITE_VK_ID_REDIRECT_URL'
 export GATEWAY_VK_ID_CLIENT_SECRET='$GATEWAY_VK_ID_CLIENT_SECRET'