added docker-compose for linux

frontend/Dockerfile

@@ -0,0 +1,25 @@
+# Stage 1: build the React app
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm ci
+
+COPY . .
+
+# These are baked into the JS bundle at build time
+ARG REACT_APP_API_URL
+ARG REACT_APP_SERIAL_URL
+ENV REACT_APP_API_URL=$REACT_APP_API_URL
+ENV REACT_APP_SERIAL_URL=$REACT_APP_SERIAL_URL
+
+RUN npm run build
+
+# Stage 2: serve with nginx
+FROM nginx:alpine
+
+COPY --from=builder /app/build /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+
+EXPOSE 80