fix(desktop): update Windows taskbar app icon

[Dante-dan]

Summary

• keep the existing window HICON update and also set Windows taskbar AppUserModel details
• persist the selected or fallback artwork as a content-addressed 256px ICO under app-owned user data so Explorer has a stable relaunch icon resource
• apply the same taskbar metadata before a new window is shown and on later icon or theme changes

Fixes #5199

Verification

• node --test apps/desktop/dist/main/__tests__/windows-taskbar-icon.test.js apps/desktop/dist/main/__tests__/app-icon.test.js apps/desktop/dist/main/__tests__/client-settings-effects.test.js (16 passed)
• biome lint on the four changed TypeScript files
• node scripts/asf-license-headers.mjs check
• git diff --check

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: OpenAI Codex traced the Windows icon surfaces, implemented the change, and added the regression tests.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

[me2seeks]

PR 5202 Review

结论

APPROVE
Windows taskbar 图标通过 per-window setAppDetails + content-addressed ICO 持久化解决，appId 与 electron-builder 的 com.maka.desktop 一致，实现与测试都扎实。