ci: publish multi-arch Docker image to GHCR on release

- build linux/amd64 + linux/arm64 via buildx
- tags: semver, major.minor, major, :beta (for -beta.* tags), :latest (for stable)
- gated on test_startup; uses GITHUB_TOKEN with packages: write
- README: point Docker quick-start at ghcr.io/datanoisetv/tinyice

Author: DatanoiseTV

.github/workflows/release.yml

@@ -7,6 +7,7 @@ on:
 
 permissions:
   contents: write
+  packages: write
 
 jobs:
   build:
@@ -139,4 +140,52 @@ jobs:
             artifacts/**/tinyice*
             checksums.txt
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  docker:
+    name: Build and Push Docker Image
+    needs: test_startup
+    runs-on: ubuntu-latest
+    if: startsWith(github.ref, 'refs/tags/')
+    steps:
+      - name: Checkout code
+        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: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository_owner }}/tinyice
+          tags: |
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=semver,pattern={{major}}
+            type=raw,value=latest,enable=${{ !contains(github.ref_name, '-') }}
+            type=raw,value=beta,enable=${{ contains(github.ref_name, '-beta') }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          build-args: |
+            VERSION=${{ github.ref_name }}
+            COMMIT=${{ github.sha }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max