add Docker support for running caldav-mcp

Introduce a multi-stage Docker build and runtime image so the server can be built and launched consistently across environments, and document build/run usage in README.

Dockerfile

@@ -0,0 +1,24 @@
+FROM node:20-bookworm-slim AS builder
+
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm ci
+
+COPY tsconfig.json ./
+COPY src ./src
+RUN npm run build
+
+FROM node:20-bookworm-slim AS runtime
+
+WORKDIR /app
+ENV NODE_ENV=production
+
+COPY package*.json ./
+RUN npm ci --omit=dev
+
+COPY --from=builder /app/dist ./dist
+
+EXPOSE 3000
+
+CMD ["node", "dist/index.js"]