ci: add CD workflow to build + push image to GHCR

Triggers on push to main and v*.*.* tags, plus manual workflow_dispatch.
Non-default branch builds tag the image by ref + short SHA; `latest` is
gated to the default branch and `stable` to version tags, so non-main
builds never clobber production tags.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: torrid-fish

.github/workflows/cd.yml

@@ -0,0 +1,68 @@
+---
+name: CD
+
+on:  # yamllint disable-line rule:truthy
+  push:
+    branches: ["main"]
+    tags: ["v*.*.*"]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  packages: write
+
+concurrency:
+  group: cd-${{ github.ref }}
+  cancel-in-progress: false
+
+jobs:
+  build-and-push:
+    name: Build and push image to GHCR
+    runs-on: ubuntu-latest
+    env:
+      REGISTRY: ghcr.io
+      # Lowercase, hardcoded: GHCR image names must be lowercase, and
+      # github.repository would be `sessatakuma/API-tools` (mixed case).
+      # Must match deploy/compose.yml's api-tools image in jpcorrect-backend.
+      IMAGE_NAME: sessatakuma/api-tools
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=sha,format=short
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=raw,value=stable,enable=${{ startsWith(github.ref, 'refs/tags/v') }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ./Dockerfile          # adjust if the api-tools Dockerfile path differs
+          platforms: linux/amd64
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max