feat: add Docker support with Dockerfile, compose, CI, and oneliner install

- Multi-stage Dockerfile (node build + nginx:alpine serve)
- nginx.conf with SPA fallback, gzip, asset caching
- docker-compose.yml for easy deployment
- GitHub Actions workflow to build & push to ghcr.io on every push
- .dockerignore to keep image lean
- Updated README with Docker-first quick start and badge

.github/workflows/docker.yml

@@ -0,0 +1,39 @@
+name: Docker
+
+on:
+  push:
+    branches: [main]
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Log in to GitHub Container Registry
+        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 }}
+          tags: |
+            type=raw,value=latest
+            type=sha,prefix=
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}