ci: simplify multi-arch build, add cache & concurrency; fix release token

- Add workflow-level concurrency to avoid overlapping releases
- Enable BuildKit cache (GHA) for faster Docker builds
- Simplify to a single multi-arch build (linux/amd64, linux/arm64)
  - Remove digest export/upload and manifest merge steps
  - Push manifest directly from buildx with tag `latest`
- Fix GitHub Release token casing to use `secrets.GITHUB_TOKEN`
- Update Dockerfile to use TARGETARCH for correct package selection
  - Pass VERSION consistently; write version to image

No functional change to runtime behavior expected; improves speed, reliability, and maintainability of the release pipeline.

.github/workflows/docker-build.yml

@@ -13,6 +13,10 @@ permissions:
   security-events: write
   statuses: read
 
+concurrency:
+  group: docker-release-${{ github.ref }}
+  cancel-in-progress: true
+
 on:
   pull_request:
     branches:
@@ -28,11 +32,6 @@ jobs:
   Docker_Build:
     name: Docker Build And Release
     runs-on: ubuntu-latest
-    strategy:
-      fail-fast: true
-      matrix:
-        arch: [amd64, arm64]
-        version: [1.12.2]
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v5
@@ -57,26 +56,13 @@ jobs:
         with:
           context: .
           build-args: |
-            ARCH=${{ matrix.arch }}
-            VERSION=${{ matrix.version }}
+            VERSION=1.12.2
           push: true
-          platforms: linux/${{ matrix.arch }}
-          outputs: type=image,name=${{ env.REGISTRY_IMAGE }},push-by-digest=true,name-canonical=true
+          platforms: linux/amd64,linux/arm64
+          tags: ${{ env.REGISTRY_IMAGE }}:latest
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
 
-      - name: Export Digests
-        run: |
-          mkdir -p /tmp/digests
-          digest="${{ steps.docker_build.outputs.digest }}"
-          touch "/tmp/digests/${digest#sha256:}"
-
-      - name: Upload digest
-        uses: actions/upload-artifact@v5
-        with:
-          name: digests-${{ matrix.arch }}
-          path: /tmp/digests/*
-          if-no-files-found: error
-          retention-days: 1
-          overwrite: true
 
   MergeRefs:
     name: Publish Multi-Arch Image And Release
@@ -85,16 +71,6 @@ jobs:
     needs:
       - Docker_Build
     steps:
-      - name: Download digests
-        uses: actions/download-artifact@v6
-        with:
-          pattern: digests-*
-          path: /tmp/digests
-          merge-multiple: true
-
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
-
       - name: Login to Registry
         id: login
         uses: docker/login-action@v3
@@ -103,25 +79,6 @@ jobs:
           username: ${{ secrets.REGISTRY_USERNAME }}
           password: ${{ secrets.REGISTRY_PASSWORD }}
 
-      - name: Docker meta
-        id: meta
-        uses: docker/metadata-action@v5
-        with:
-          images: ${{ env.REGISTRY_IMAGE }}
-          tags: |
-            # set latest tag for default branch
-            # https://github.com/docker/metadata-action#latest-tag
-            type=raw,value=latest,enable={{is_default_branch}}
-
-      - name: Create manifest list and push
-        working-directory: /tmp/digests
-        run: |
-          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
-            $(printf '${{ env.REGISTRY_IMAGE }}@sha256:%s ' *)
-      - name: Inspect image
-        run: |
-          docker buildx imagetools inspect ${{ env.REGISTRY_IMAGE }}:${{ steps.meta.outputs.version }}
-
       - name: Generate SBOM
         uses: anchore/sbom-action@v0
         id: sbom
@@ -167,7 +124,7 @@ jobs:
         id: release
         if: ${{ steps.changelog.outputs.skipped == 'false' }}
         env:
-          GITHUB_TOKEN: ${{ secrets.github_token }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with:
           tag_name: ${{ steps.changelog.outputs.tag }}
           name: ${{ steps.changelog.outputs.tag }}