Splash green Site Kit font colour

## Bug Description

While testing SFR3 Splash page, I noticed G Site Kit whole logo appears at the top of the dashboard.
However, I want to flag that the colour for Site Kit is currently `#5F6561` and on Figma, it's #161B18.
And also, the exit button is still here. It should not.

Actuals:

Figma:

## Steps to reproduce

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

## Screenshots

## Additional Context

- PHP Version:
- OS: [e.g. iOS]
- Browser: [e.g. chrome, safari]
- Plugin Version: [e.g. 22]
- Device: [e.g. iPhone6]

---------------

_Do not alter or remove anything below. The following sections will be managed by moderators only._

## Acceptance criteria

*

## Implementation Brief

* [ ]

### Test Coverage

*

## QA Brief

*

## Changelog entry

*

Start by reproducing the SFR3 Splash page and comparing the dashboard logo and exit button with the supplied screenshots and Figma reference. Locate the frontend entry point for this Splash page, then verify that the Site Kit text uses #161B18, the exit button is absent, and the rendered result matches the reference.

Written by the indexing model from the issue text.