Add internal development webhook configuration

docs/ocsentinel-deployment.md

@@ -75,6 +75,13 @@ This writes:
 
 - `C:\ProgramData\OCSentinel\secrets\ocsentinel-upload-secret.dat`
 
+## Development Upload
+
+For the internal development environment, copy
+`config/ocsentinel-client.dev.example.json` to the installed client config
+path and use its HTTP webhook URL. Production clients must use the HTTPS
+configuration with the public Sentinel domain instead.
+
 ## Current Manual Release State
 
 As of July 16, 2026, the first manual release is already published: