TEST_PROD and Blue-Green

The pipeline updates TEST_PROD (testing stack) via the deploy:test_prod job: pull frontend and backend by digest, start new color, health-check, switch proxy, stop old color. One deployment at a time (resource_group).

Live production (e.g. register.hacklahoma.org) is not updated by CI; it is updated on the server (pull, rebuild, restart) or by your own deploy process. TEST_PROD is for validation and staging; production is a separate step.