fix: Update Docker config for Next.js frontend

- Updated Dockerfile.frontend to use Next.js instead of React CRA
- Multi-stage build for optimized image size
- Use NEXT_PUBLIC_API_URL instead of REACT_APP_API_URL
- Updated docker-compose.yml to pass correct env variable
- Frontend now starts with 'npm start' instead of serve

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

e-voting-system/docker-compose.yml

@@ -51,8 +51,7 @@ services:
       context: .
       dockerfile: docker/Dockerfile.frontend
       args:
-        REACT_APP_API_URL: http://backend:8000
-        CACHEBUST: ${CACHEBUST:-1}
+        NEXT_PUBLIC_API_URL: http://backend:8000
     container_name: evoting_frontend
     ports:
       - "${FRONTEND_PORT:-3000}:3000"

e-voting-system/docker/Dockerfile.frontend

@@ -1,34 +1,36 @@
+# Build stage
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+# Copy package files
+COPY frontend/package*.json ./
+
+# Install dependencies
+RUN npm ci
+
+# Copy source code
+COPY frontend/ .
+
+# Build argument for API URL (Next.js uses NEXT_PUBLIC_)
+ARG NEXT_PUBLIC_API_URL=http://backend:8000
+ENV NEXT_PUBLIC_API_URL=${NEXT_PUBLIC_API_URL}
+
+# Build Next.js app
+RUN npm run build
+
+# Production stage
 FROM node:20-alpine
 
 WORKDIR /app
 
-# Copier package.json
-COPY frontend/package*.json ./
-
-# Installer dépendances
-RUN npm install --legacy-peer-deps
-
-# Copier code source
-COPY frontend/ .
-
-# Clean previous builds
-RUN rm -rf build/
-
-# Build argument for API URL
-ARG REACT_APP_API_URL=http://backend:8000
-ENV REACT_APP_API_URL=${REACT_APP_API_URL}
-
-# Force rebuild timestamp (bust cache)
-ARG CACHEBUST=1
-ENV CACHEBUST=${CACHEBUST}
-
-# Build avec npm run build (CRA standard)
-RUN npm run build
-
-# Installer serve pour servir la build
-RUN npm install -g serve
+# Copy only necessary files from builder
+COPY --from=builder /app/public ./public
+COPY --from=builder /app/.next ./.next
+COPY --from=builder /app/node_modules ./node_modules
+COPY --from=builder /app/package.json ./package.json
 
 EXPOSE 3000
 
-# Servir la build
-CMD ["serve", "-s", "build", "-l", "3000"]
+# Start Next.js in production mode
+CMD ["npm", "start"]