[Task] Auto-updater for Windows

[shellen]

Part of: [Epic] Add Windows support (#66)

Summary

Configure Tauri's built-in updater for Windows. Needs a separate update manifest or shared one with platform-specific assets.

Notes

• Tauri v2 updater already supports Windows
• Main work is configuring the update manifest with Windows-specific asset URLs
• May share manifest with macOS or use platform-specific endpoints

Acceptance Criteria

• Windows app checks for updates on launch
• Update manifest includes Windows assets
• Update downloads and installs correctly on Windows

Estimate: ~0.5 day
Priority: Nice-to-have