Add Dockerization stage and setup in GitLab CI pipelines

frontend/.gitlab-ci.yml

@@ -1,8 +1,48 @@
+image: node:22@sha256:f6b9c31ace05502dd98ef777aaa20464362435dcc5e312b0e213121dcf7d8b95
+
 stages:
   - frontend_build
+  - dockerize
+
+cache:
+  key: ${CI_COMMIT_REF_SLUG}
+  paths:
+    - node_modules/
+    - .next/cache/
+
+variables:
+  NEXT_PUBLIC_ENV: "production"
+  OUTPUT_DIR: ".next"
+  PROJECT_NAME: $CI_PROJECT_NAME
+  DOCKER_IMAGE: "registry.boomlab.party/rheinsw/$CI_PROJECT_NAME"
+
+# Reusable block for docker build & push
+.dockerize_script: &dockerize_script
+  - |
+    RAW_TAG="$CI_COMMIT_REF_NAME"
+    TAG="${RAW_TAG//\//_}"  # replace "/" with "_"
+    echo "Sanitized tag: $TAG"
+    docker build -t $DOCKER_IMAGE:$TAG -f Dockerfile .
+
+    if [[ "$RAW_TAG" == "dev" || "$RAW_TAG" == "production" ]]; then
+      echo "Pushing Docker image $DOCKER_IMAGE:$TAG"
+      docker push $DOCKER_IMAGE:$TAG
+    else
+      echo "Skipping Docker push for non-dev or production branch: $RAW_TAG"
+    fi
 
 frontend_build_job:
   stage: frontend_build
-  image: node:22@sha256:f6b9c31ace05502dd98ef777aaa20464362435dcc5e312b0e213121dcf7d8b95
   script:
-    - echo "Building frontend project"
+    - npm install
+    - npx next build
+    - npm run lint
+
+dockerize_frontend:
+  stage: dockerize
+  image: docker:20.10@sha256:2967f0819c84dd589ed0a023b9d25dcfe7a3c123d5bf784ffbb77edf55335f0c
+  before_script:
+    - echo "$CI_REGISTRY_PASSWORD" | docker login "$CI_REGISTRY" -u "$CI_REGISTRY_USER" --password-stdin
+  script: *dockerize_script
+  needs:
+    - job: frontend_build_job