Refactor Dockerfile to streamline backend package installation

Dockerfile

@@ -18,8 +18,8 @@ WORKDIR /app-new
 ENV NODE_ENV=production
 ENV PORT=3000
 
-COPY app-new/backend/package*.json backend/
-RUN cd backend && npm install --omit=dev
+COPY app-new/backend/package*.json ./
+RUN npm ci --omit=dev
 
 COPY --from=build /app-new/dist dist
 COPY --from=build /app-new/templates templates