fix(panel): expose toggle aria attributes

[xonaib]

Summary

• Adds Button inputs for aria-controls and aria-expanded so they are rendered on the native button element.
• Wires Panel's toggle button to those inputs while keeping the existing host attributes in place.
• Updates Panel accessibility tests to assert against the native button instead of the p-button host.

Testing

• pnpm --filter @openng/optimus-ui exec ng test optimus-ui --include=src/panel/panel.spec.ts --watch=false --browsers=ChromeHeadless --progress=false
• pnpm --filter @openng/optimus-ui build

Fixes #626