Fix: keep Dashboard switch names readable in the light theme

[SandObserver]

Summary

• Add a light-theme resting fill of #3A3A3C for the Dashboard switch keychain names (.nm). They kept the dark theme's #D6D6DB and measured 1.4:1 on the white card.
• Add a test that the light-theme fill clears 4.5:1 on white.

Testing
All green, including the Docker build. Added 1 test for the light-theme name contrast.

Changelog

Fixed

• Dashboard switch names are readable in the light theme.

Checklist

• Stays within the project constraints: one container, no runtime dependencies, no build step (see CONTRIBUTING.md).
• Tests added or updated for new logic, and the full suite, lint, and typechecks pass.
• Docs updated if behavior or configuration changed.