docs: document plugin properties migrated from env vars

Per-plugin management docs now describe the properties introduced by the env-var-to-property migration in PR #8498, and stale prose and command-output examples that still referenced the old `DOKKU_*` names have been refreshed. The deprecated env vars table moves out of `environment-variables.md` and into the 0.38.0 migration guide, where it functions as a one-time pointer for upgrading users rather than ongoing reference material.

docs/deployment/application-management.md

@@ -13,6 +13,7 @@ apps:lock <app>                                # Locks an app for deployment
 apps:locked <app>                              # Checks if an app is locked for deployment
 apps:rename <old-app> <new-app>                # Rename an app
 apps:report [<app>] [<flag>]                   # Display report about an app
+apps:set [--global] <app> <key> (<value>)      # Set or clear an apps property for an app
 apps:unlock <app>                              # Unlocks an app for deployment
 ```
 
@@ -78,6 +79,20 @@ Once created, you can configure the application as normal, and deploy the applic
 - Create and link datastores.
 - Set environment variables.
 
+### Disabling automatic app creation
+
+By default, pushing to a git remote for an app that does not yet exist on the Dokku host will cause the app to be created automatically. On shared or production hosts this may be undesirable - operators may prefer that an explicit `apps:create` is required first. The `disable-autocreation` global property controls this behavior:
+
+```shell
+dokku apps:set --global disable-autocreation true
+```
+
+While set, pushes targeting an app that does not exist will be rejected. The default behavior may be restored by passing an empty value:
+
+```shell
+dokku apps:set --global disable-autocreation
+```
+
 ### Removing a deployed app
 
 In some cases, you may need to destroy an application, whether it is because the application is temporary or because it was misconfigured. In these cases, you can use the `apps:destroy` command. Performing any destructive actions in Dokku requires confirmation, and this command will ask for the name of the application being deleted before doing so.