fix: use npm install instead of npm ci (no package-lock.json)

Co-Authored-By: Paperclip <noreply@paperclip.ing>

frontend/Dockerfile

@@ -1,7 +1,7 @@
 FROM node:20-alpine AS build
 WORKDIR /app
 COPY package*.json ./
-RUN npm ci
+RUN npm install
 COPY . .
 RUN npm run build