chore: add npm install command in Dockerfiles for both backend and frontend

backend/Dockerfile

@@ -4,6 +4,8 @@
 FROM node:22-alpine AS builder
 WORKDIR /app
 
+RUN npm install -g npm@latest
+
 # Kopiera backend-filer
 COPY package.json ./
 COPY prisma ./prisma

frontend/Dockerfile

@@ -1,5 +1,6 @@
 FROM node:22-alpine AS deps
 WORKDIR /app
+RUN npm install -g npm@latest
 COPY package.json ./
 RUN npm install