v2.2.8.4

Add light mode styling for studio embed requests

- Introduced a new function `ai_gateway_is_studio_embed_request` to check for studio embed requests in the admin area.
- Added `ai_gateway_studio_admin_light_mode` to apply light mode styles when in studio embed mode.
- Updated the admin head to include light mode styles for various elements.
- Modified the iframe source in `studio.js` to include a query parameter for studio mode.