Audit and fix light/dark mode support across all key screens

[Lakes41]

Difficulty: Intermediate
Type: UI/UX

Background
The README's Key Features list explicitly promises "a beautiful, accessible UI built with NativeWind, optimized for both light and dark environments."

Problem
It's easy for individual screens (especially newer ones like the access scanner or guild detail) to drift out of sync with dark-mode styling if colors are hardcoded instead of using NativeWind's dark: variant classes, leading to poor contrast or invisible text in one mode.

Expected outcome
Every screen under app/ renders correctly and legibly in both light and dark mode, verified against the OS-level appearance setting, with no hardcoded colors that break in either mode.

Suggested implementation

• Audit each screen under app/ for hardcoded hex/rgb color values instead of NativeWind's theme-aware utility classes.
• Replace hardcoded colors with dark:-variant Tailwind classes consistent with the project's existing design tokens (check tailwind.config.js for any custom color palette already defined).
• Manually test by toggling the OS appearance setting (or Expo Go's dev menu) and confirming legibility on every screen.
• Document any intentionally fixed-color elements (e.g., a brand logo) as an exception.

Acceptance criteria

• All screens under app/ verified legible in both light and dark mode
• No hardcoded colors remain outside documented exceptions
• Verified on at least one iOS and one Android device/simulator

Likely affected files/directories

• app/
• tailwind.config.js

[EngrEOOnoja]

I'd like to take this on. I'll audit every screen under app/ for hardcoded colors, replace them with the existing dark:-variant classes from the project's design tokens, manually verify legibility across light/dark mode on both iOS and Android, and document any intentional fixed-color exceptions.

[grantfox-oss]

🦊 GrantFox — @EngrEOOnoja has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #234)
2. Your PR will be reviewed by the Adamantine-guild maintainers

Good luck! Track your progress on GrantFox.