chore: make use of $PROJECT_SLUG in Gitlab CI

.gitlab-ci.yml

@@ -30,7 +30,7 @@ build:
     - apk add git
     - yarn install
   script:
-    - export NEXT_PUBLIC_BASE_PATH="" && [[ "$CI_COMMIT_REF_NAME" != "main" ]] && export NEXT_PUBLIC_BASE_PATH="/entwicklungsportal/!$CI_MERGE_REQUEST_IID"
+    - export NEXT_PUBLIC_BASE_PATH="" && [[ "$CI_COMMIT_REF_NAME" != "main" ]] && export NEXT_PUBLIC_BASE_PATH="/$PROJECT_SLUG/!$CI_MERGE_REQUEST_IID"
     - echo $NEXT_PUBLIC_BASE_PATH
     - yarn export
   artifacts:
@@ -49,7 +49,7 @@ deploy:preview:
     name: preview/$CI_MERGE_REQUEST_IID
     on_stop: stop:preview
     auto_stop_in: 2 week
-    url: https://preview.docs.fitko.dev/entwicklungsportal/!$CI_MERGE_REQUEST_IID
+    url: https://preview.docs.fitko.dev/$PROJECT_SLUG/!$CI_MERGE_REQUEST_IID
   rules:
     - if: $CI_COMMIT_BRANCH != $CI_DEFAULT_BRANCH
   needs: