Add custom image and push action

.forgejo/workflows/build.yml

@@ -0,0 +1,49 @@
+name: Build and Publish Docker Image
+
+on:
+  push:
+    branches:
+      - main
+
+env:
+  REGISTRY: stackit-solutions.git.onstackit.cloud
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push:
+    runs-on: lxc
+    permissions:
+      packages: write
+      contents: read
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Docker
+        run: |
+          curl -fsSL https://get.docker.com -o get-docker.sh
+          sudo sh get-docker.sh
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract base image version
+        id: version
+        run: |
+          VERSION=$(sed -n 's/^FROM .*:\(.*\)$/\1/p' Dockerfile)
+          echo "version=$VERSION" >> $GITHUB_OUTPUT
+
+      - name: Build and push Docker image
+        id: push
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.version.outputs.version }}