[FEATURE] Custom Theme elements

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

There are only two themes offered and both hurt my eyes. I greatly wish to control the background and text colors of the window. page bg, chat bubble colors, font colors.

Proposed Solution

Add a 3rd option under Themes and allow users to select colors and save as a theme.

Alternative Solutions

There is none

Priority

Medium - Would be very helpful

Feature Category

Other

Use Case Example

Right now I would go and make a sepia toned theme with low contrast that would soothe my eyes during the long sessions. I already use computers and Claude all day at work. I'm 58 years old and my eyes need to be treated gently.

Additional Context

_No response_