Add Dockerfile and GitHub Actions workflow to publish to ghcr.io

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: traviswheeler

.github/workflows/docker.yml

@@ -0,0 +1,41 @@
+name: Build and push Docker image
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract version from tag
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository_owner }}/blimmp
+          tags: |
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=raw,value=latest
+
+      - name: Build and push
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}

Dockerfile

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+FROM python:3.10-slim
+
+WORKDIR /app
+COPY . .
+RUN pip install --no-cache-dir .