[Task] Mac-native theme override

[kantord]

Description

This PR adds a generic color theme override system: #2263 Which has the actual themeing implementation and a single data source, a user-level JSON.

But doesn't include MacOS native system-level settings support.

Acceptance Criteria

• Implement Electron systemPreferences support on Mac:https://www.electronjs.org/docs/latest/api/system-preferences
• this allows for system-level override, not just user level

Priority

Medium

Task Type

Feature

Additional Context

No response