Improve Theme Dropdown UI

Description:

When clicking on the Theme dropdown in the Pong Game, the different theme options are not clearly visible. Currently, they only become visible when hovered, which makes the UI confusing and unattractive for players. This affects the overall game experience since themes should be easy to preview and select.

Steps to Reproduce:

- Open the Pong Game.
- Click on the Theme dropdown menu.
- Notice that theme options are not clearly visible until hovered.

Current Behavior:

- Theme options are not visible by default after opening the dropdown.
- Visibility relies on hover, reducing usability.

Expected Behavior:

- All theme options should be clearly visible immediately upon opening the dropdown.
- The dropdown should follow the same modern glowing theme style as the rest of the game.
- Options should have good contrast with the background, ensuring readability.

Proposed Solution / Enhancements:

- Improve contrast and background color of dropdown options.
- Use consistent typography with the game’s design.
- Add hover, focus, and active states for a smooth experience.
- Ensure dropdown styling matches the Pong Game’s glowing, futuristic theme.

Checklist:

- Fix visibility issue of theme options.
- Improve contrast & readability.
- Add hover, focus, and active states.
- Ensure consistency with Pong Game UI theme.