ci(workflows): add pr-build workflow for dev/test container images

- Introduces a new GitHub Actions workflow that automatically builds and pushes multi-arch Docker images for pull requests
- Images are tagged with the PR number (e.g., dev-pr-123) for easy identification
- Uses GHCR as the container registry with proper authentication via GITHUB_TOKEN
- Implements BuildKit cache optimization for faster builds
- Supports both linux/amd64 and linux/arm64 platforms

.github/workflows/pr-build.yml

@@ -0,0 +1,50 @@
+name: PR Dev/Test Container
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write   # ✅ needed for GHCR push
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Login to GHCR
+        uses: docker/login-action@v2
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Extract metadata for PR builds
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v4
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=raw,value=dev-pr-${{ github.event.pull_request.number }}
+
+      # Build and push multi-arch dev image
+      - name: Build and push
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max