Remove Backend API URL section from SKILL.md

Removed section about Backend API URL configuration.

.github/skills/settings-management/SKILL.md

@@ -37,11 +37,3 @@ Define in plugin's `config.json` manifest under the settings section.
 ## Environment Override
 
 Use `APP_CONF_OVERRIDE` environment variable for settings that must be set before startup.
-
-## Backend API URL
-
-For Codespaces, set `BACKEND_API_URL` to your Codespace URL:
-
-```
-BACKEND_API_URL=/server
-```