feat: add Dockerfile and GitHub Actions workflow for building and publishing Docker image

.github/workflows/docker.yml

@@ -0,0 +1,98 @@
+name: Build and Publish Docker Image
+
+on:
+  push:
+    branches:
+      - main
+      - master
+    paths:
+      - "unshackle/core/__init__.py"
+      - "Dockerfile"
+      - "pyproject.toml"
+      - "uv.lock"
+      - ".github/workflows/docker.yml"
+    tags:
+      - "v*"
+  pull_request:
+    branches:
+      - main
+      - master
+    paths:
+      - "unshackle/core/__init__.py"
+      - "Dockerfile"
+      - "pyproject.toml"
+      - "uv.lock"
+      - ".github/workflows/docker.yml"
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Extract version from __init__.py
+        id: version
+        run: |
+          VERSION=$(grep -oP '__version__ = "\K[^"]+' unshackle/core/__init__.py)
+          echo "version=$VERSION" >> $GITHUB_OUTPUT
+          echo "major_minor=$(echo $VERSION | cut -d. -f1-2)" >> $GITHUB_OUTPUT
+          echo "major=$(echo $VERSION | cut -d. -f1)" >> $GITHUB_OUTPUT
+          echo "Extracted version: $VERSION"
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Container Registry
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=ref,event=pr
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=semver,pattern={{major}}
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=raw,value=v${{ steps.version.outputs.version }},enable={{is_default_branch}}
+            type=raw,value=${{ steps.version.outputs.version }},enable={{is_default_branch}}
+            type=raw,value=${{ steps.version.outputs.major_minor }},enable={{is_default_branch}}
+            type=raw,value=${{ steps.version.outputs.major }},enable={{is_default_branch}}
+
+      - name: Show planned tags
+        run: |
+          echo "Planning to create the following tags:"
+          echo "${{ steps.meta.outputs.tags }}"
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+      - name: Test Docker image
+        if: github.event_name != 'pull_request'
+        run: |
+          docker run --rm ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest env check