BUG: Hardcoded Background and Text Colors in AuthScreenWrapper Prevents Theme Adaptation

### Is there an existing issue for this?

- [x] I have searched the existing issues

### What happened?

**What happened?**
The `AuthScreenWrapper` widget currently utilizes hardcoded color values that prevent the authentication screens (Login, Signup, etc.) from correctly adapting to the application's theme modes. Specifically:

* The `Scaffold` background is hardcoded to a dark hex value (`0xFF1A1A1A`), which ignores the `lightTheme` scaffold background color (`0xFFF0F0F0`) defined in the theme configuration.
* The title text within the wrapper is hardcoded to `Colors.white`. While this is visible in dark mode, it will lead to significant accessibility and visibility issues when the background switches to the light theme's grey/white palette.

**Steps to Reproduce:**

1. Set the application to `ThemeMode.light`.
2. Navigate to the Login or Signup screen.
3. Observe that the background remains dark despite the light theme setting, and text contrast is not managed through the theme's `textTheme`.

**Expected Behavior:**
The `AuthScreenWrapper` should use `Theme.of(context).scaffoldBackgroundColor` for its background and utilize theme-based text styles (such as `displayLarge` or `headlineMedium`) for its typography to ensure a consistent experience in both light and dark modes.

## Screen recording

https://github.com/user-attachments/assets/330ca3f7-6702-40b7-8acc-cad1872c4919

### Record

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- [x] I want to work on this issue