Fixes the web widget select dropdown styling in dark mode so native
select options remain readable against the widget's dark UI.
Closes
None
## Screenshots
Previous state:
<img width="426" height="764" alt="Previous dark mode dropdown issue"
src="https://github.com/user-attachments/assets/812fa88c-ae5a-4769-be14-748fbbaf7dfe"
/>
Current state:
<img width="1210" height="610" alt="Current dark mode dropdown styling"
src="https://github.com/user-attachments/assets/0ec9b6d7-025d-4b97-b43e-ef026857f9c4"
/>
## How to test
1. Enable the web widget pre-chat form with a list/select field.
2. Load the widget with dark mode enabled.
3. Open the select field and verify the select control and option text
remain readable in dark mode.
## What changed
- Adds light/dark color-scheme handling for widget native selects.
- Applies explicit option background and text colors so dark-mode select
options do not inherit unreadable colors from the browser popup.
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Co-authored-by: iamsivin <iamsivin@gmail.com>
