feat(ci): add workflow to publish bun Docker image to GHCR (#333)

Adds containers/bun.Dockerfile (bun:1-alpine + git) and a GitHub Actions
workflow that builds and pushes ghcr.io/decocms/mcps/bun on changes to
the Dockerfile or via manual trigger.

Made-with: Cursor

Author: guitavano

.github/workflows/publish-docker.yml

@@ -0,0 +1,45 @@
+name: Publish Docker Image
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+    paths:
+      - "containers/bun.Dockerfile"
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout repository
+        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 }}/bun
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=sha,prefix=sha-
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: ./containers
+          file: ./containers/bun.Dockerfile
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}

containers/bun.Dockerfile

@@ -0,0 +1,3 @@
+FROM oven/bun:1-alpine
+
+RUN apk add --no-cache git