fix (gmail): Update unread emails to match background and hover of read emails

[a-moth]

🗒 Checklist 🗒

• I have read and followed Catppuccin's userstyle contributing guidelines.

• I used AI (or AI-assistance) for this change.

🔧 What does this fix? 🔧

Added the hover effect and background colour to unread email class.

🔍 Reproduction Steps 🔍

Before	After
Unread emails had a background matching the background of the page behind, not the same background as read emails. Unread emails missing hover effect.	Unread and read emails have the same background and hover effect.

[WalkQuackBack]

While we are assessing Google's long-term plans with Gmail styling, and the newer components moving towards using the Google Material 3 design system, Gmail pull requests are currently pending.