Fix some for docker

DOCKER.md

@@ -33,6 +33,13 @@ DATABASE_URL=postgresql://goldbank:...@db:5432/goldbank?schema=public
 PORT=3000
 ```
 
+A second copy on the **same server** is a separate Dokploy application (its own
+domains, passwords, and `JWT_SECRET`). Do not set `container_name` in this file:
+those names are global in Docker, and a fixed `goldbank_db` collides with the
+first copy. Give the second app its own `EXTERNAL_DB_PORT` (for example `5434`
+if `5433` is already taken). Volumes stay separate because Dokploy uses a
+different Compose project name for each application.
+
 ## Domains (container ports)
 
 | Service | Domain | Port |