Add GitHub Actions workflow and update docker-compose to use GHCR

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

Dockerfile

@@ -0,0 +1,11 @@
+FROM node:26-alpine
+WORKDIR /app
+COPY package*.json ./
+RUN npm ci --omit=dev
+COPY . .
+ENV NODE_ENV=production
+ENV DATA_DIR=/app/data
+EXPOSE 3000
+HEALTHCHECK --interval=30s --timeout=10s --retries=3 \
+  CMD wget -q -O - http://localhost:3000/health || exit 1
+CMD ["node", "server.js"]