fix: ensure .env file is copied during Docker build process

Author: kshitijrajsharma

frontend/Dockerfile.prod

@@ -5,6 +5,7 @@
 FROM node:22 AS builder
 WORKDIR /app
 COPY package.json pnpm-lock.yaml ./
+COPY .env ./.env
 RUN npm install -g pnpm
 RUN pnpm install --force
 COPY . .