Make SITE_URL and AUTH_SECRET configurable via environment variables for any deployment

docker-compose.yml

@@ -1,6 +1,10 @@
 services:
   nlcc-itinerary:
-    build: .
+    build:
+      context: .
+      args:
+        - SITE_URL=${SITE_URL:-https://nlcc.rydertech.us}
+        - AUTH_SECRET=${AUTH_SECRET:-change-this-secret-in-production}
     container_name: nlcc-itinerary
     ports:
       - "3002:3000"
@@ -8,6 +12,6 @@ services:
       - ./data:/app/data
     environment:
       - NODE_ENV=production
-      - AUTH_SECRET=d8c7c1735fc853b807c1bccce791b054
-      - SITE_URL=https://nlcc.rydertech.us
+      - AUTH_SECRET=${AUTH_SECRET:-change-this-secret-in-production}
+      - SITE_URL=${SITE_URL:-https://nlcc.rydertech.us}
     restart: unless-stopped