Update desktop app icon assets / 更新桌面应用图标资源

[SivanCola]

Summary

• Replace the desktop app PNG icon with a cleaner blue-background single-mark design.
• Add the SVG source asset and keep it tracked through the existing build-asset ignore rules.
• Regenerate the Windows ICO from the same source so macOS, Linux, and Windows use consistent app icon artwork.

Verification

• Validated the PNG and ICO asset formats and dimensions with platform tools.
• Generated a temporary ICNS successfully from the updated PNG-derived iconset.
• Ran the desktop module Windows tray icon test command; on macOS the Windows-tagged test is skipped as expected.

Full Wails packaging was not run locally.

[SivanCola]

approve