🐛 fix(frontend): update Dockerfile to use node:20-alpine as base image for frontend build

✨ feat(frontend): add support for BACKEND_URL environment variable in nginx.conf to configure backend URL
📝 chore(frontend): add start-nginx.sh script to replace placeholder in nginx.conf with actual BACKEND_URL and start nginx

src/frontend/start-nginx.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+# Replace the placeholder with the actual value
+sed -i "s|__BACKEND_URL__|$BACKEND_URL|g" /etc/nginx/conf.d/default.conf
+
+
+# Start nginx
+exec nginx -g 'daemon off;'