feat: add Ravenwood theme to TUI

[raythurman2386]

Description

This PR adds the Ravenwood theme, a refined forest-inspired color palette designed for high legibility and a professional aesthetic. It also updates the TUI to use Ravenwood as the default fallback theme instead of Everforest.

Key changes:

• Defined Ravenwood theme struct with specific colors for background, foreground, accents, and file actions.
• Registered "ravenwood" in the global Themes map.
• Added Ravenwood to the AllThemes() slice.
• Updated GetTheme to return Ravenwood as the default theme.

Fixes # (issue)

Type of change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update (added a new theme option)

How Has This Been Tested?

• Visual Verification: Launched straw with theme = "ravenwood" and verified all UI components (Header, Lists, Logs, Footer) render correctly.
• Fallback Verification: Launched straw with an invalid theme name in the config and verified it correctly falls back to the Ravenwood theme.
• Color Contrast: Verified contrast ratios for action styles (ActionMove, ActionCopy, etc.) against the new background.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes