updated 3 tier structure

docker-compose.yml

@@ -2,6 +2,8 @@ services:
   db:
     image: docker.io/library/postgres:16-alpine
     restart: unless-stopped
+    # NOTE: Change POSTGRES_PASSWORD in production. Consider using Docker secrets or
+    # a managed PostgreSQL service instead of local credentials.
     environment:
       POSTGRES_DB: kmountain
       POSTGRES_USER: postgres
@@ -14,6 +16,8 @@ services:
       timeout: 5s
       retries: 5
 
+  # NOTE: Update KMTN_CORS_ORIGINS in production to your actual domain(s).
+  # Set KMTN_DATABASE_URL to your managed PostgreSQL connection if not using the local db service.
   api:
     build:
       context: ./backend