move old docker guide

Author: nicktrn

docs/open-source-self-hosting.mdx

@@ -1,8 +1,10 @@
 ---
-title: "Self-hosting"
-description: "You can self-host Trigger.dev on your own infrastructure."
+title: "Docker (legacy)"
+description: "You can self-host Trigger.dev on your own infrastructure using Docker."
 ---
 
+<Tip>This guide is for v3, you can find the v4 guide [here](/self-hosting/docker).</Tip>
+
 <Warning>Security, scaling, and reliability concerns are not fully addressed here. This guide is meant for evaluation purposes and won't result in a production-ready deployment.</Warning>
 
 <Note>This guide is for Docker only. We don't currently provide documentation for Kubernetes.</Note>