Add GitHub Actions workflow to build and publish Docker images to GHCR

Author: Gamedirection

.github/workflows/docker-publish.yml

@@ -0,0 +1,77 @@
+name: Build & Publish Docker Images
+
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - 'v*'
+
+env:
+  REGISTRY: ghcr.io
+  FRONTEND_IMAGE: ghcr.io/gamedirection/open-trivia-frontend
+  BACKEND_IMAGE:  ghcr.io/gamedirection/open-trivia-backend
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Log in to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Read frontend version
+        id: version
+        run: |
+          VERSION=$(node -p "require('./frontend/package.json').version")
+          echo "value=$VERSION" >> "$GITHUB_OUTPUT"
+
+      # ── Frontend ────────────────────────────────────────────────────────────
+
+      - name: Frontend metadata
+        id: frontend-meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.FRONTEND_IMAGE }}
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=raw,value=v${{ steps.version.outputs.value }}
+            type=semver,pattern={{version}},enable=${{ startsWith(github.ref, 'refs/tags/') }}
+
+      - name: Build & push frontend
+        uses: docker/build-push-action@v5
+        with:
+          context: ./frontend
+          push: true
+          tags: ${{ steps.frontend-meta.outputs.tags }}
+          labels: ${{ steps.frontend-meta.outputs.labels }}
+
+      # ── Backend ─────────────────────────────────────────────────────────────
+
+      - name: Backend metadata
+        id: backend-meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.BACKEND_IMAGE }}
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=raw,value=v${{ steps.version.outputs.value }}
+            type=semver,pattern={{version}},enable=${{ startsWith(github.ref, 'refs/tags/') }}
+
+      - name: Build & push backend
+        uses: docker/build-push-action@v5
+        with:
+          context: ./backend
+          push: true
+          tags: ${{ steps.backend-meta.outputs.tags }}
+          labels: ${{ steps.backend-meta.outputs.labels }}