+ added license headers

The mode setting is deprecated (and the build process says
so for quite a long time).

They mention to switch to 'ssr' setting (either true or false).
As we use it as an spa application, we set this property to false.

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

* fix "Unexpected trailing comma"

* 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

- enable hash mode in nuxt router

- use relative paths to _nuxt directory