Update the old Google G wherever it still shows

## Feature Description

#11791 updated the Google "G" in `logo-g.svg`, `logo-sitekit.svg`, and `Google_Icon::XML`. Five places still show the old one

- `assets/svg/graphics/sign-in-with-google.svg`, on the **Sign in with Google** row in **Settings** and on that module's setup screen.
- `assets/svg/graphics/sign-in-with-google-setup.svg`, on the Sign in with Google setup form.
- `assets/blocks/sign-in-with-google/icon.svg`, on the **Sign in with Google** block in the editor. `Edit.js` imports it.
- `assets/svg/graphics/splash-screenshot.svg`, on the splash screen.
- `2025-12-01-site-kit-logo.png`, in the email report. `Email_Assets::ASSETS` names the file and `https://sitekit-static.withgoogle.com/` serves it, so this one needs a new image uploaded under a new dated name.

Update all five to the new mark.

⚠️ Google's own script draws the **Sign in with Google** button on four more screens, so nothing here reaches them:

- The button inside a post.
- The WordPress login screen.
- A user's own profile screen.
- The module's setup preview.

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## Acceptance criteria

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## Implementation Brief

* [ ]

### Test Coverage

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## QA Brief

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## Changelog entry

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Compare the updated assets from #11791, then inspect the five named files: the three SVGs, the block icon imported by Edit.js, and 2025-12-01-site-kit-logo.png. Check Email_Assets::ASSETS for the report logo and the existing static-hosting convention. Done means all five locations use the new mark, with the email logo uploaded under a new dated name.

Written by the indexing model from the issue text.