Add cv backendurl environment variable to prepare ufz ci in master for the final cv-backend-integration branch merge and change variable name for sms backend

Fix ufz deployment configuration and rename configuration parameter  BACKEND_URL to BACKEND_HOST_URL to distinguish between host part and later added base url

* add required environment vars to ci and docker compose
* fix path in docker file
* add base path from environment to nuxt config

- OIDC integration
- Gitlab CI with deployment specific settings
- Set base url from environment