Revamped Autoupdate Behavior

[pierremtb]

Scope

Started the discussion at https://kittycadworkspace.slack.com/archives/C04KFV6NKL0/p1773255698662779

Tentative requirements:

• the auto update shall run on app start if previously downloaded, or on user click on download
• the download shall happen in the background (no change from today)
• a notificiation less intrusive than the current toast shall appear on download completed

UI mockup needs

Yes, cc @franknoirot. I'm thinking about a status bar item for this? Much like the Download app button on web

Dependencies

None.