feat: Fixing Dockerfile for non-root user and app building

Dockerfile

@@ -2,14 +2,17 @@ FROM node:20-alpine
 
 WORKDIR /app
 
-COPY package.json package-lock.json* ./
-RUN npm install --omit=dev
+COPY package.json package-lock.json ./
+RUN npm ci --omit=dev && node -e "require('express')"
 
 COPY server.js ./
 COPY src ./src
 COPY public ./public
 COPY locales ./locales
 
+RUN chown -R node:node /app
+USER node
+
 ENV PORT=3000
 EXPOSE 3000