Fix template error: add os to settings save response context

- Added 'os': os to dashboard_settings_save template context
- Fixes jinja2.exceptions.UndefinedError: 'os' is undefined
- Template needs os.environ to get USER for tor hidden service path
- GET endpoint already had it, POST endpoint was missing it

main.py

@@ -4674,6 +4674,7 @@ async def dashboard_settings_save(
         "request": request,
         "session": request.session,
         "config": aisbf_config,
+        "os": os,
         "success": "Settings saved successfully! Restart server for changes to take effect."
     }
     )