feat: add Dockerfile and CI workflow for Docker image publishing

.dockerignore

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+node_modules
+.git
+.gitignore
+*.md
+.env*
+.wrangler
+dist
+coverage
+*.log
+.github

.github/workflows/docker.yml

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+name: Docker Build & Push
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*.*.*"]
+  pull_request:
+    branches: [main]
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      # Multi-arch support: linux/amd64 and linux/arm64
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      # Login only on push, not on PRs from forks
+      - name: Login to GHCR
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Auto-generates tags: latest, v1.2.3, v1.2, sha-abc1234
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=sha,prefix=sha-
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        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
+          provenance: true
+          sbom: true

Dockerfile

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+# ─── Stage 1: Builder ────────────────────────────────────────────────────────
+FROM node:22-slim AS builder
+WORKDIR /app
+COPY package*.json ./
+RUN npm ci --frozen-lockfile
+COPY . .
+RUN npm run build --if-present
+
+# ─── Stage 2: Runner (final image) ───────────────────────────────────────────
+# node:22-slim (Debian) instead of Alpine: workerd binary requires glibc
+FROM node:22-slim
+
+# Apply security patches + install runtime dependencies:
+# - dumb-init: PID 1 process manager for correct SIGTERM handling in Kubernetes
+# - wget: used by the HEALTHCHECK to ping the HTTP endpoint
+# - ca-certificates: required by workerd for HTTPS calls to GitHub (payload fetch)
+RUN apt-get update && apt-get upgrade -y --no-install-recommends && \
+    apt-get install -y --no-install-recommends \
+      dumb-init \
+      wget \
+      ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+# Create a dedicated non-root user with fixed UID/GID 1001
+# -m creates the home directory /home/appuser
+# wrangler writes logs to ~/.config/.wrangler/ so the home dir is required
+RUN groupadd -g 1001 appgroup && \
+    useradd -u 1001 -g appgroup -m -s /bin/sh appuser
+
+WORKDIR /app
+COPY --chown=appuser:appgroup package*.json ./
+
+# npm ci runs here (not copied from builder) to ensure platform-native workerd binary
+# --include=optional ensures workerd is downloaded as an optional dependency
+# wrangler@latest fixes the mkdtemp bug present in the bundled 4.42.0
+RUN npm ci --frozen-lockfile --include=optional && \
+    npm install wrangler@latest && \
+    mkdir -p /app/.wrangler-tmp && \
+    chown -R appuser:appgroup /app
+
+# Copy only what is needed at runtime from the builder stage
+COPY --from=builder --chown=appuser:appgroup /app/app ./app
+COPY --chown=appuser:appgroup wrangler.toml .
+
+# wrangler needs HOME to locate ~/.config/.wrangler/
+ENV HOME=/home/appuser
+# Disable telemetry
+ENV WRANGLER_SEND_METRICS=false
+# Prevent wrangler from opening a browser tab
+ENV BROWSER=none
+# Use /app/.wrangler-tmp instead of /tmp to avoid noexec mount issues in Docker Desktop
+ENV TMPDIR=/app/.wrangler-tmp
+
+USER appuser
+EXPOSE 8787
+
+# Check every 30s that the server is responding
+# start-period gives wrangler 20s to boot before health checks begin
+HEALTHCHECK --interval=30s --timeout=10s --start-period=20s --retries=3 \
+  CMD wget -qO- http://localhost:8787/ || exit 1
+
+# dumb-init as PID 1 for correct signal handling in Kubernetes
+ENTRYPOINT ["dumb-init", "--"]
+# --ip 0.0.0.0: required to be reachable outside the container (default is 127.0.0.1)
+# --local: runs without Cloudflare authentication
+CMD ["npx", "wrangler", "dev", "--ip", "0.0.0.0", "--port", "8787", "--local"]