feat: add config fields for overriding theme colors

[jahvon]

Summary

Adds the colorOverride field to the user config file. This allows overriding the lipgloss colors used in the TUI's theme

[codecov]

Codecov Report

Attention: Patch coverage is 19.29825% with 46 lines in your changes missing coverage. Please review.

Project coverage is 37.40%. Comparing base (e7ef96a) to head (7d2d4a7).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/context/context.go	19.29%	34 Missing and 12 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #203      +/-   ##
==========================================
- Coverage   37.63%   37.40%   -0.23%     
==========================================
  Files          77       77              
  Lines        6523     6579      +56     
==========================================
+ Hits         2455     2461       +6     
- Misses       3609     3648      +39     
- Partials      459      470      +11     

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