ci: add Docker image release workflow

.github/workflows/release-docker.yml

@@ -0,0 +1,64 @@
+name: Release Docker Image
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - docker/Dockerfile
+      - bindings/python/pyproject.toml
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Image tag (e.g. v1.0.1). Leave empty to use version from pyproject.toml'
+        required: false
+        type: string
+
+permissions:
+  contents: read
+
+jobs:
+  build-and-push:
+    name: Build and push Docker image
+    if: github.repository == 'lightseekorg/smg'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Determine version tag
+        id: version
+        run: |
+          if [[ -n "${{ inputs.tag }}" ]]; then
+            VERSION="${{ inputs.tag }}"
+          else
+            VERSION=$(grep -m1 '^version = ' bindings/python/pyproject.toml | sed 's/version = "\(.*\)"/\1/')
+          fi
+          echo "version=${VERSION}" >> "$GITHUB_OUTPUT"
+          echo "Using version: ${VERSION}"
+
+      - 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 Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: docker/Dockerfile
+          push: true
+          tags: |
+            lightseekorg/smg:${{ steps.version.outputs.version }}
+            lightseekorg/smg:latest
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          platforms: linux/amd64,linux/arm64