fix: #3637905 Use a PNG logo in HTML emails instead of the SVG site logo

Issue: https://www.drupal.org/i/3637905

HTML emails use the SVG site logo, which Gmail and Outlook do not show. This ships config/easy_email_theme.settings.yml pointing the Easy Email Theme logo at the Rightup Theme - Bootstrap 5 PNG (themes/contrib/vartheme_bs5_rightup/logo-email.png), the same fix as Varbase Starter (#3637289).

It is a config file, not a simpleConfigUpdate action in recipe.yml like the Gin, Gin Login and Navigation logos: Easy Email Theme ships no default settings, so easy_email_theme.settings does not exist when the recipe runs and simpleConfigUpdate cannot create it. Recipes only create config that does not exist yet, so sites that already set a logo keep it.

Needs the Rightup Theme - Bootstrap 5 PNG (#3637902) released first. Until then the path points at a missing file and emails show no logo, as today.

Testing

1. Install The Rightup with the Rightup Theme - Bootstrap 5 MR in place.
2. drush config:get easy_email_theme.settings shows use_default: false and the PNG path.
3. Send a password reset email and open it in Mailpit: the logo <img> is logo-email.png.

AI-Generated: Yes

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