added v3 to v4 migreation note about IP change

Author: isshaddad

docs/migrating-from-v3.mdx

@@ -48,6 +48,10 @@ Note that between steps 4 and 5, runs triggered with the v4 package will continu
   concurrency will return to normal.
 </Warning>
 
+<Note>
+  When migrating from v3 to v4, our infrastructure IPs may change. If you use IP allowlisting (e.g. for databases or APIs), update your allowlists before or immediately after switching to v4 to avoid connectivity issues or downtime.
+</Note>
+
 ## Migrate using AI
 
 Use the prompt in the accordion below to help you migrate your v3 tasks to v4. The prompt gives good results when using Claude 4 Sonnet. You’ll need a relatively large token limit.