- Serve GET /settings as JSON by removing duplicate HTML route (use /settings/page for the standalone UI).
- Save global_brightness via PUT; broadcast to connected drivers; push saved level when outbound WS connects.
- Zones UI loads brightness from GET /settings only (no localStorage).
- Bump led-driver submodule for settings.save on brightness with save flag.
- Extend API doc and endpoint tests for global_brightness.
Co-authored-by: Cursor <cursoragent@cursor.com>
