fix(BridgeUI): <SelectChain /> Arrow Right button not visible in light mode if no wallet is connected

[kyrers]

Describe the bug

The ArrowRight /> button in the <SelectChain /> component is not visible in light mode if no wallet is connected.
This happens because the button is disabled if !$signer.

I'd be more than glad to solve this issue for you, but I do want to hear your preference before making a PR.
For what it's worth, I do agree that the button should be disabled in this instance. As I see it, the easiest option that does not modify anything else, as far as I can tell, is creating a specific style for [data-theme="light"] .btn:disabled svg and modifying the color property. In the screenshots, I used dark-color-6 as it seemed the closest to the "Approve" color, but that it's still visible.

I will of course solve it any way you wish.

Steps to reproduce

1. Go to the Brigde UI;
2. Disconnect your wallet;
3. Switch to light mode.

Additional context

Problem

Proposed Fix - Light Mode

Proposed Fix - Dark Mode