Fix Nginx template environment variable syntax for Docker deployment

docker-compose.yml

@@ -10,6 +10,9 @@ services:
       - "80:80"
     depends_on:
       - backend
+    environment:
+      - BACKEND_HOST=backend
+      - BACKEND_PORT=3001
     networks:
       - app-network
 

nginx-template.conf

@@ -11,7 +11,7 @@ server {
 
     # Proxy API requests to the backend server
     location /api/ {
-        proxy_pass http://${BACKEND_HOST:-backend}:${BACKEND_PORT:-3001}/;
+        proxy_pass http://$BACKEND_HOST:$BACKEND_PORT/;
         proxy_http_version 1.1;
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection 'upgrade';