Studio settings should be in dark mode for UI consistency

#### Reason/Context
Please try answering few of those questions
- Why we need this improvement?
The rest of AsyncAPI Studio uses a dark theme, but the Studio Settings modal remains in light mode, which feels visually inconsistent.
- How will this change help?
Adding dark mode support to the settings section will ensure a consistent and cohesive UI experience across the entire Studio.

#### Description
Currently, the Studio Settings modal uses a light theme even when the rest of the application is in dark mode.

Current behavior:

can be like this

The settings modal should follow the same dark theme as the rest of the Studio to maintain visual consistency throughout the application.

The issue names no files, tests, or entry points. Locate the Studio Settings modal and compare it with the existing dark-themed Studio UI; the work is done when the modal follows the same dark theme while retaining its current settings behavior.

Written by the indexing model from the issue text.