ci: add GitHub Actions workflow for Docker image build & push 🐳

.github/workflows/docker-build.yml

@@ -0,0 +1,65 @@
+name: 🐳 Build & Push Docker Image
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*"]
+  pull_request:
+    branches: [main]
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository_owner }}/picoclaw
+
+jobs:
+  build:
+    name: 🏗️ Build Docker Image
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      # ── Checkout ──────────────────────────────
+      - name: 📥 Checkout repository
+        uses: actions/checkout@v4
+
+      # ── Docker Buildx ─────────────────────────
+      - name: 🔧 Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      # ── Login to GHCR ─────────────────────────
+      - name: 🔑 Login to GitHub Container Registry
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # ── Metadata (tags & labels) ──────────────
+      - name: 🏷️ Extract Docker 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=sha,prefix=
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=raw,value={{date 'YYYYMMDD-HHmmss'}},enable={{is_default_branch}}
+
+      # ── Build & Push ──────────────────────────
+      - name: 🚀 Build and push Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          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
+          platforms: linux/amd64,linux/arm64