Update Node.js to v21

Dockerfile

@@ -1,5 +1,5 @@
 # 1. Install dependencies only when needed
-FROM node:20-alpine AS deps
+FROM node:21-alpine AS deps
 # Check https://github.com/nodejs/docker-node/tree/b4117f9333da4138b03a546ec926ef50a31506c3#nodealpine to understand why libc6-compat might be needed.
 RUN apk add --no-cache libc6-compat
 
@@ -8,7 +8,7 @@ COPY package.json yarn.lock ./
 RUN yarn install --frozen-lockfile
 
 # 2. Rebuild the source code only when needed
-FROM node:20-alpine AS builder
+FROM node:21-alpine AS builder
 WORKDIR /app
 COPY --from=deps /app/node_modules ./node_modules
 COPY . .
@@ -16,7 +16,7 @@ COPY . .
 RUN yarn build
 
 # 3. Production image, copy all the files and run next
-FROM node:20-alpine AS runner
+FROM node:21-alpine AS runner
 WORKDIR /app
 
 ENV NODE_ENV=production