fix: Dockerfile - force dev deps, use explicit nest path

Dockerfile

@@ -1,16 +1,19 @@
 # Stage 1: Build backend
 FROM node:20-alpine AS backend-builder
 WORKDIR /app/backend
+# Force dev deps install regardless of any injected NODE_ENV
+ENV NODE_ENV=development
 COPY backend/package*.json ./
-RUN npm ci --legacy-peer-deps
+RUN npm ci --legacy-peer-deps --include=dev
 COPY backend/ .
-RUN npm run build
+RUN ./node_modules/.bin/nest build
 
 # Stage 2: Build frontend
 FROM node:20-alpine AS frontend-builder
 WORKDIR /app/frontend
+ENV NODE_ENV=development
 COPY frontend/package*.json ./
-RUN npm ci --legacy-peer-deps
+RUN npm ci --legacy-peer-deps --include=dev
 COPY frontend/ .
 ENV NEXT_PUBLIC_API_URL=/api-backend
 ENV NEXT_TELEMETRY_DISABLED=1