Add initial Windows port for the desktop app

[Jonohobs]

Summary

• add an initial Windows port for the desktop app
• add a Windows CI build that produces downloadable installer artifacts
• make the packaging compatibility adjustments needed for the Windows build path

Notes

This PR is intended as a Windows porting contribution so the existing desktop app can also build and launch on Windows.

To get the Windows path working cleanly, I made a couple of packaging-oriented adjustments:

• limit an unsigned Windows packaging workaround to the Windows path that needed it
• update ICO generation so the generated Windows icon includes the higher-resolution size Electron Builder expects for Windows installers

These changes are intended to make the Windows build work reliably from source and to make that path reproducible in CI.

Windows build updates

• add a desktop_windows job to .github/workflows/ci.yml
• scope an unsigned packaging workaround to the Windows path only
• disable executable editing for unsigned Windows builds
• update scripts/generate-brand-assets.py so generated ICOs include the sizes expected by the Windows packaging toolchain
• regenerate the affected favicon and Windows icon assets

Validation

• built the Windows NSIS installer successfully on Windows
• verified the installer completed and produced an installed app under %LOCALAPPDATA%\\Programs\\okcode-desktop
• launched the installed Windows app successfully after installation
• parsed the updated CI YAML locally

[vercel]

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[BunsDev]

Thanks for this Windows desktop port, @Jonohobs ✨ Merging it together with the Windows icon packaging fix now.

[BunsDev]

I replayed the Windows desktop changes cleanly onto current main and merged them via #32 to avoid dragging in stale branch regressions. Thanks again for the original work here, @Jonohobs ✨

[BunsDev]

Superseded by #32, which rebased and merged the Windows desktop work cleanly onto current main. Thanks again @Jonohobs ✨