feat: Add CI environment setup and verification workflows with Docker support

.github/workflows/build-ci.yaml

@@ -0,0 +1,54 @@
+name: Build CI Environment
+
+on:
+  workflow_dispatch:
+    inputs:
+      image_tag:
+        description: 'Tag for the CI image (e.g., latest)'
+        required: true
+        default: 'latest'
+
+env:
+  # OVERRIDE_REGISTRY can be set as a secret to override the default registry (e.g., for testing with a private registry). Else '' will be used, which defaults to ghcr.io for github.com and the GitHub server domain for self-hosted GitHub instances.
+  OVERRIDE_REGISTRY: ${{ secrets.OVERRIDE_REGISTRY }}
+
+permissions:
+  contents: read
+  packages: write
+
+concurrency:
+  group: build-ci
+  cancel-in-progress: true
+
+jobs:
+  build-ci-image:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup CI metadata
+        id: setup
+        uses: ./.github/actions/setup-ci-metadata
+        with:
+          registry: ${{ env.OVERRIDE_REGISTRY }}
+          image_tag: ${{ github.event.inputs.image_tag }}
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v4
+        with:
+          registry: ${{ steps.setup.outputs.registry }}
+          username: ${{ secrets.GITHUB_USERNAME || github.actor }}
+          password: ${{ secrets.OVERRIDE_GITHUB_TOKEN || secrets.GITHUB_TOKEN }}
+
+      - name: Build and push Docker image for CI
+        uses: docker/build-push-action@v3
+        with:
+          context: .
+          file: .github/docker/ci.Dockerfile
+          push: true
+          tags: |
+            ${{ steps.setup.outputs.image_tag }}
+            ${{ steps.setup.outputs.latest_tag }}