FEAT: Windows Theme & Dark Mode Support

[ahkrichards]

Caution

Developed on a fork with dotnet 10 tooling: ahkrichards/feature/dotnet-10

Not tested against .NET 4.8 toolchain.

If there is interest in this feature, I can invest more time to adding for Mac as well as ensuring compatibility with .NET 4.8. I simply added dotnet 10 toolchain for the purposes of quick starting my local development without need to add augment my env with explicit .NET 4.8 support.

This PR adds a dark mode spike for the Windows GUI, including theme switching, improved contrast, and Windows title bar integration. The UI now supports Follow System / Light / Dark modes, with consistent styling across menus, inputs, and dialogs.

Key Changes

• Added a theme manager and persisted theme setting (Follow System / Light / Dark).
• Applied dark theme styling across the WinForms UI and dialogs.
• Improved menu contrast (including left margin) to match legacy readability.
• Fixed initial text color application before controls become enabled.
• Tuned input/list borders and button contrast for dark mode.
• Applied Windows title bar dark mode when supported (safe fallback on unsupported OS).

Notes

• Title bar theming uses DWM attributes on Windows 10/11; no-op fallback on older systems.
• mac GUI intentionally untouched.

Preview

Initial load:

New View menu and Theme menu items:

Loaded song:

Backwards compatible / maintains previous theme: