UI Enhancements: AppBar & Settings Page Color Improvements

[davidetarsi]

This pull request introduces UI refinements to improve visual consistency and user experience.

Changes made:

• AppBar Background: Changed the AppBar background color to white, following a clean and modern style inspired by Facebook.
• Icon Colors: Updated the colors of icons in the AppBar and Popup Menu to match Facebook's official blue, ensuring a consistent and recognizable design.
• Settings Page Tiles: Enhanced the appearance of toggle tiles in the Settings page, ensuring they display the correct blue color when toggled, even in dark mode.

Benefits:

• Improved UI consistency by adopting a cleaner color scheme.
• Enhanced user experience with more intuitive and visually appealing toggle states in the Settings page.
• Dark mode compatibility for a better user experience across different themes.