build(frontend): update docker image to use production env

frontend/Dockerfile

@@ -1,9 +1,13 @@
-FROM node:20-alpine
-
+# --- Build stage ---
+FROM node:20-alpine AS build
 WORKDIR /app
 COPY package*.json ./
 RUN --mount=type=cache,target=/root/.npm npm ci
-
 COPY . .
-EXPOSE 5173
-CMD ["npm", "run", "dev"]
+RUN npm run build
+
+# --- Production stage ---
+FROM nginx:1.27-alpine AS prod
+COPY --from=build /app/dist /usr/share/nginx/html
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]