Restore Old Admin Colors

WordPress 7.0 changed the default admin color scheme to "Modern", renaming the long-standing classic palette to "Fresh" and migrated existing users over to the new default. This plugin quietly restores the classic Fresh scheme for every user, exactly once, without taking away anyone's freedom to switch back later.

• Sets the color scheme to Fresh for newly registered users.
• Migrates each existing user from "Modern" (or no preference) back to "Fresh" the next time they visit the dashboard, exactly once.
• Leaves users who already chose another scheme (Light, Blue, Midnight, Ocean, Coffee, Ectoplasm, Sunrise, etc.) completely alone.
• Restores the classic "Fresh" look on the login screen too, the blue WordPress logo, the classic blue submit button, and the classic blue input focus ring.
• Cleans up after itself when deactivated, reverting every migrated user back to "Modern" and removing its own user metadata.
• No settings page, no public front-end assets, no scheduled jobs, no mass updates on activation. The login styles are printed only while the plugin is active and disappear the moment it is deactivated or deleted.