Publish Docker image to GHCR on main builds

Add a Docker workflow that builds on PRs and pushes to
ghcr.io/chewbaccalakis/rfid-database on main (latest + sha) and v* tags.
Drop the redundant docker-build job from CI.

.github/workflows/ci.yml

@@ -22,11 +22,3 @@ jobs:
       - run: npm run build
         env:
           AUTH_SECRET: ci-build-secret-at-least-32-characters
-
-  docker:
-    name: docker-build
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - name: Build production image
-        run: docker build -t rfid-database:ci .

.github/workflows/docker.yml

@@ -0,0 +1,60 @@
+name: Docker
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*"]
+  pull_request:
+    branches: [main]
+
+env:
+  REGISTRY: ghcr.io
+  # GHCR requires lowercase image names
+  IMAGE_NAME: ghcr.io/chewbaccalakis/rfid-database
+
+jobs:
+  build-and-push:
+    name: build-and-push
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      attestations: write
+      id-token: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GitHub Container Registry
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels)
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.IMAGE_NAME }}
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=sha,prefix=sha-,format=short
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ./Dockerfile
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max