all these changes

backend/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:18-alpine
+FROM node:20-alpine
 
 # Set working directory
 WORKDIR /app
@@ -6,8 +6,17 @@ WORKDIR /app
 # Copy package files
 COPY package*.json ./
 
-# Install dependencies
-RUN npm install --only=production --silent
+# Build-time flag to include dev dependencies for local images
+ARG NODE_ENV=production
+ENV NODE_ENV=${NODE_ENV}
+
+# Install dependencies (omit dev deps for production images)
+RUN if [ "$NODE_ENV" = "development" ]; then \
+      npm ci --include=dev --silent; \
+    else \
+      npm ci --omit=dev --silent; \
+    fi && \
+    npm cache clean --force
 
 # Copy source code
 COPY . .