Adjust dark mode to lighter tones for better readability

- Updated background colors from near-black to dark gray tones
- Primary bg: #0a0a0b -> #1e1e22 (VS Code/Discord-inspired)
- Secondary bg: #111113 -> #252529
- Tertiary/elevated/hover backgrounds proportionally lightened
- Border colors made slightly more visible
- Fixed hardcoded rgba in Layout.css header
- All text colors maintain WCAG AA contrast ratios

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added internal proxy configuration for npm, pip, helm, and apt (#51)
 
 ### Changed
+- Adjusted dark mode color palette to use lighter background tones for better readability and reduced eye strain (#52)
 - Improved pod naming: Orchard pods now named `orchard-{env}-server-*` for clarity (#51)
 
 ### Fixed