Add an app to a computer

Body: { name, command, cwd?, port?, restart?, run_as?, enabled?, env?, secret_env? }. name: 1-32 lowercase letters, digits and hyphens, unique on the computer. command runs with bash in cwd (default the user’s home), after /root/.env and the app’s variables are loaded; values are used as typed. restart: always (default), on-failure (started again after a non-zero exit; an exit in its first 3 seconds counts as a failed start and is retried) or no (once per boot). run_as: root by default. port: what the app listens on, unique on the computer; the computer’s own ports (22, 3389, 5900-5999, 6080-6099, 8080, 9000) are refused. secret_env values are stored encrypted and never returned (only their names, in secret_env_keys). Applied at once when the computer is running (apply.state "applied"); otherwise saved and applied when it next runs ("pending"). Never wakes the computer. At most 20 apps a computer.