fix: use Debian node for build stages to fix rollup musl Alpine bug

Dockerfile

@@ -1,15 +1,16 @@
-# Stage 1: Build frontend
+# Stage 1: Build frontend (use Debian-based node to avoid Alpine musl/rollup issues)
-FROM node:20-alpine AS frontend-build
+FROM node:20 AS frontend-build
 WORKDIR /app/frontend
+ENV NODE_ENV=development
 COPY frontend/package*.json ./
-# Remove lock file and reinstall fresh to avoid rollup musl bug on Alpine
 RUN rm -f package-lock.json && npm install --legacy-peer-deps
 COPY frontend/ ./
 RUN npm run build
 
 # Stage 2: Build backend
-FROM node:20-alpine AS backend-build
+FROM node:20 AS backend-build
 WORKDIR /app/backend
+ENV NODE_ENV=development
 COPY backend/package*.json ./
 RUN npm install
 COPY backend/ ./