feat: update frontend Dockerfile with multi-stage build

frontend/Dockerfile

@@ -1,23 +1,13 @@
-# Use Node.js 22 LTS as base image
-FROM node:22-alpine
-
-# Set working directory
+# Build stage
+FROM node:22-alpine AS builder
 WORKDIR /app
-
-# Copy package files
 COPY package*.json ./
-
-# Install dependencies
 RUN npm ci
-
-# Copy source code
 COPY . .
-
-# Build the application
 RUN npm run build
 
-# Expose port 8080
-EXPOSE 8080
-
-# Run the application
-CMD ["npm", "run", "preview"]
+# Production stage
+FROM nginx:alpine
+COPY --from=builder /app/dist /usr/share/nginx/html
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]