build: use node:20-alpine to match fleet pattern

Dockerfile

@@ -1,12 +1,8 @@
-FROM node:22-slim
-
+FROM node:20-alpine
 WORKDIR /app
-
-COPY package.json ./
-RUN npm install --omit=dev
-
-COPY src/ src/
-
+ENV NODE_ENV=production
+COPY package*.json ./
+RUN npm install --omit=dev && npm cache clean --force
+COPY src ./src
 EXPOSE 9222
-
 CMD ["node", "src/http-server.js"]