FEAT: Tauri v2 Desktop Shell

[github-actions]

🎯 Objective

Implement the core functionality for the Tauri v2 Desktop Shell feature.

📦 Crate

$(@{id=tauri-shell; name=Tauri v2 Desktop Shell; phase=5; crate=apps/desktop; passes=False; tests=System.Object[]; last_updated=}.crate)

📚 Description from features.json

Tauri v2 Desktop Shell

This task was automatically generated by the Planner Agent based on the project's feature manifest. The goal is to implement this feature and ensure all related tests pass.