Significantly improve Dockerfile

https://github.com/vercel/next.js/tree/canary/examples/with-docker

todoblue/Dockerfile

@@ -1,14 +1,25 @@
-FROM node:20.5.1
+FROM node:20 AS base
 
+FROM base AS builder
 WORKDIR /usr/src/todoblue
 
 COPY ./package.json ./yarn.lock ./
-RUN yarn install
+RUN yarn install --frozen-lockfile
 
 COPY ./ ./
 RUN yarn run build
 
-ENTRYPOINT ["yarn", "run", "start", "--port=8081"]
+
+FROM base AS runner
+WORKDIR /usr/lib/todoblue
+
+COPY --from=builder /usr/src/todoblue/public ./public
+COPY --from=builder /usr/src/todoblue/.next/standalone ./
+COPY --from=builder /usr/src/todoblue/.next/static ./static
+
+ENV NODE_ENV production
+
+ENTRYPOINT ["node", "server.js"]
 CMD []
 
 LABEL org.opencontainers.image.title="Todocolors Blue"
@@ -17,4 +28,4 @@ LABEL org.opencontainers.image.licenses="AGPL-3.0-or-later"
 LABEL org.opencontainers.image.url="https://github.com/Steffo99/todocolors"
 LABEL org.opencontainers.image.authors="Stefano Pigozzi <me@steffo.eu>"
 
-EXPOSE 8081
+EXPOSE 3000

todoblue/next.config.js

@@ -1,4 +1,6 @@
 /** @type {import('next').NextConfig} */
-const nextConfig = {}
+const nextConfig = {
+	output: "standalone",
+}
 
 module.exports = nextConfig