fix: replace npm ci with npm install (no lockfile yet)

client/Dockerfile

@@ -4,7 +4,7 @@ FROM node:20-alpine AS builder
 WORKDIR /app
 
 COPY package.json package-lock.json* ./
-RUN npm ci
+RUN npm install
 
 COPY . .
 RUN npm run build

server/Dockerfile

@@ -3,7 +3,7 @@ FROM node:20-alpine AS deps
 
 WORKDIR /app
 COPY package.json package-lock.json* ./
-RUN npm ci --omit=dev
+RUN npm install --omit=dev
 
 # ── Stage 2 : runtime ─────────────────────────────────────────────────────────
 FROM node:20-alpine