feat: new scrollbar style and fix some bug in dark mode

[Innei]

WHAT

🤖 Generated by Copilot at f8209b4

This pull request adds a new feature to allow users to customize the theme color of the xLog app, and enhances the scrollbar styling with the theme color. It introduces a new CSS variable --theme-color in src/css/variables.css and applies it to the webkit scrollbar in src/css/tailwind.css.

🤖 Generated by Copilot at f8209b4

The xLog app has a new feature
To change its main color with a switcher
It uses --theme-color
And adjusts to the user
And the webkit scrollbar gets a makeover

WHY

Fix #330

HOW

🤖 Generated by Copilot at f8209b4

• Add custom styles for the webkit scrollbar using theme color variables (link)
• Define a new CSS variable --theme-color that can be dynamically changed by the theme switcher script or the system settings (link, link)

[vercel]

@Innei is attempting to deploy a commit to the RSS3 Team on Vercel.

A member of the Team first needs to authorize it.

[Innei]

[zsakvo]

I think we need to consider Firefox as well.