feat(docker): update Node.js version to 24.15.0 in Dockerfile and test workflow

backend/Dockerfile

@@ -1,25 +1,26 @@
 # Byggas från backend-mappen: docker build -t recipe-api:local .
 
 # Stage 1: Bygg applikationen
-FROM node:22-alpine AS builder
+FROM node:24.15.0-alpine AS builder
 WORKDIR /app
 
 # Kopiera backend-filer
 COPY package.json ./
+COPY package-lock.json ./
 COPY prisma ./prisma
 COPY src ./src
 COPY tsconfig.json ./
 COPY nest-cli.json ./
 
-# Köra npm install
-RUN npm install
+# Köra npm ci för reproducerbara builds
+RUN npm ci
 
 RUN npx prisma generate
 RUN npm test
 RUN npm run build
 
 # Stage 2: Kör applikationen
-FROM node:22-alpine AS runner
+FROM node:24.15.0-alpine AS runner
 WORKDIR /app
 ENV NODE_ENV=production